1 \input texinfo @c -*-texinfo-*-
2 @c Copyright 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,
3 @c 1999, 2000, 2001, 2002, 2003, 2004, 2005
4 @c Free Software Foundation, Inc.
7 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
8 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
25 @c readline appendices use @vindex, @findex and @ftable,
26 @c annotate.texi and gdbmi use @findex.
30 @c !!set GDB manual's edition---not the same as GDB version!
31 @c This is updated by GNU Press.
34 @c !!set GDB edit command default editor
37 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
39 @c This is a dir.info fragment to support semi-automated addition of
40 @c manuals to an info tree.
41 @dircategory Software development
43 * Gdb: (gdb). The GNU debugger.
47 This file documents the @sc{gnu} debugger @value{GDBN}.
50 This is the @value{EDITION} Edition, of @cite{Debugging with
51 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
52 Version @value{GDBVN}.
54 Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,@*
55 1999, 2000, 2001, 2002, 2003, 2004, 2005@*
56 Free Software Foundation, Inc.
58 Permission is granted to copy, distribute and/or modify this document
59 under the terms of the GNU Free Documentation License, Version 1.1 or
60 any later version published by the Free Software Foundation; with the
61 Invariant Sections being ``Free Software'' and ``Free Software Needs
62 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
63 and with the Back-Cover Texts as in (a) below.
65 (a) The Free Software Foundation's Back-Cover Text is: ``You have
66 freedom to copy and modify this GNU Manual, like GNU software. Copies
67 published by the Free Software Foundation raise funds for GNU
72 @title Debugging with @value{GDBN}
73 @subtitle The @sc{gnu} Source-Level Debugger
75 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
76 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
80 \hfill (Send bugs and comments on @value{GDBN} to bug-gdb\@gnu.org.)\par
81 \hfill {\it Debugging with @value{GDBN}}\par
82 \hfill \TeX{}info \texinfoversion\par
86 @vskip 0pt plus 1filll
87 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995,
88 1996, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
89 Free Software Foundation, Inc.
91 Published by the Free Software Foundation @*
92 59 Temple Place - Suite 330, @*
93 Boston, MA 02111-1307 USA @*
96 Permission is granted to copy, distribute and/or modify this document
97 under the terms of the GNU Free Documentation License, Version 1.1 or
98 any later version published by the Free Software Foundation; with the
99 Invariant Sections being ``Free Software'' and ``Free Software Needs
100 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
101 and with the Back-Cover Texts as in (a) below.
103 (a) The Free Software Foundation's Back-Cover Text is: ``You have
104 freedom to copy and modify this GNU Manual, like GNU software. Copies
105 published by the Free Software Foundation raise funds for GNU
111 @node Top, Summary, (dir), (dir)
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN} Version
120 Copyright (C) 1988-2005 Free Software Foundation, Inc.
123 * Summary:: Summary of @value{GDBN}
124 * Sample Session:: A sample @value{GDBN} session
126 * Invocation:: Getting in and out of @value{GDBN}
127 * Commands:: @value{GDBN} commands
128 * Running:: Running programs under @value{GDBN}
129 * Stopping:: Stopping and continuing
130 * Stack:: Examining the stack
131 * Source:: Examining source files
132 * Data:: Examining data
133 * Macros:: Preprocessor Macros
134 * Tracepoints:: Debugging remote targets non-intrusively
135 * Overlays:: Debugging programs that use overlays
137 * Languages:: Using @value{GDBN} with different languages
139 * Symbols:: Examining the symbol table
140 * Altering:: Altering execution
141 * GDB Files:: @value{GDBN} files
142 * Targets:: Specifying a debugging target
143 * Remote Debugging:: Debugging remote programs
144 * Configurations:: Configuration-specific information
145 * Controlling GDB:: Controlling @value{GDBN}
146 * Sequences:: Canned sequences of commands
147 * TUI:: @value{GDBN} Text User Interface
148 * Interpreters:: Command Interpreters
149 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
150 * Annotations:: @value{GDBN}'s annotation interface.
151 * GDB/MI:: @value{GDBN}'s Machine Interface.
153 * GDB Bugs:: Reporting bugs in @value{GDBN}
154 * Formatting Documentation:: How to format and print @value{GDBN} documentation
156 * Command Line Editing:: Command Line Editing
157 * Using History Interactively:: Using History Interactively
158 * Installing GDB:: Installing GDB
159 * Maintenance Commands:: Maintenance Commands
160 * Remote Protocol:: GDB Remote Serial Protocol
161 * Agent Expressions:: The GDB Agent Expression Mechanism
162 * Copying:: GNU General Public License says
163 how you can copy and share GDB
164 * GNU Free Documentation License:: The license for this documentation
173 @unnumbered Summary of @value{GDBN}
175 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
176 going on ``inside'' another program while it executes---or what another
177 program was doing at the moment it crashed.
179 @value{GDBN} can do four main kinds of things (plus other things in support of
180 these) to help you catch bugs in the act:
184 Start your program, specifying anything that might affect its behavior.
187 Make your program stop on specified conditions.
190 Examine what has happened, when your program has stopped.
193 Change things in your program, so you can experiment with correcting the
194 effects of one bug and go on to learn about another.
197 You can use @value{GDBN} to debug programs written in C and C@t{++}.
198 For more information, see @ref{Supported languages,,Supported languages}.
199 For more information, see @ref{C,,C and C++}.
202 Support for Modula-2 is partial. For information on Modula-2, see
203 @ref{Modula-2,,Modula-2}.
206 Debugging Pascal programs which use sets, subranges, file variables, or
207 nested functions does not currently work. @value{GDBN} does not support
208 entering expressions, printing values, or similar features using Pascal
212 @value{GDBN} can be used to debug programs written in Fortran, although
213 it may be necessary to refer to some variables with a trailing
216 @value{GDBN} can be used to debug programs written in Objective-C,
217 using either the Apple/NeXT or the GNU Objective-C runtime.
220 * Free Software:: Freely redistributable software
221 * Contributors:: Contributors to GDB
225 @unnumberedsec Free software
227 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
228 General Public License
229 (GPL). The GPL gives you the freedom to copy or adapt a licensed
230 program---but every person getting a copy also gets with it the
231 freedom to modify that copy (which means that they must get access to
232 the source code), and the freedom to distribute further copies.
233 Typical software companies use copyrights to limit your freedoms; the
234 Free Software Foundation uses the GPL to preserve these freedoms.
236 Fundamentally, the General Public License is a license which says that
237 you have these freedoms and that you cannot take these freedoms away
240 @unnumberedsec Free Software Needs Free Documentation
242 The biggest deficiency in the free software community today is not in
243 the software---it is the lack of good free documentation that we can
244 include with the free software. Many of our most important
245 programs do not come with free reference manuals and free introductory
246 texts. Documentation is an essential part of any software package;
247 when an important free software package does not come with a free
248 manual and a free tutorial, that is a major gap. We have many such
251 Consider Perl, for instance. The tutorial manuals that people
252 normally use are non-free. How did this come about? Because the
253 authors of those manuals published them with restrictive terms---no
254 copying, no modification, source files not available---which exclude
255 them from the free software world.
257 That wasn't the first time this sort of thing happened, and it was far
258 from the last. Many times we have heard a GNU user eagerly describe a
259 manual that he is writing, his intended contribution to the community,
260 only to learn that he had ruined everything by signing a publication
261 contract to make it non-free.
263 Free documentation, like free software, is a matter of freedom, not
264 price. The problem with the non-free manual is not that publishers
265 charge a price for printed copies---that in itself is fine. (The Free
266 Software Foundation sells printed copies of manuals, too.) The
267 problem is the restrictions on the use of the manual. Free manuals
268 are available in source code form, and give you permission to copy and
269 modify. Non-free manuals do not allow this.
271 The criteria of freedom for a free manual are roughly the same as for
272 free software. Redistribution (including the normal kinds of
273 commercial redistribution) must be permitted, so that the manual can
274 accompany every copy of the program, both on-line and on paper.
276 Permission for modification of the technical content is crucial too.
277 When people modify the software, adding or changing features, if they
278 are conscientious they will change the manual too---so they can
279 provide accurate and clear documentation for the modified program. A
280 manual that leaves you no choice but to write a new manual to document
281 a changed version of the program is not really available to our
284 Some kinds of limits on the way modification is handled are
285 acceptable. For example, requirements to preserve the original
286 author's copyright notice, the distribution terms, or the list of
287 authors, are ok. It is also no problem to require modified versions
288 to include notice that they were modified. Even entire sections that
289 may not be deleted or changed are acceptable, as long as they deal
290 with nontechnical topics (like this one). These kinds of restrictions
291 are acceptable because they don't obstruct the community's normal use
294 However, it must be possible to modify all the @emph{technical}
295 content of the manual, and then distribute the result in all the usual
296 media, through all the usual channels. Otherwise, the restrictions
297 obstruct the use of the manual, it is not free, and we need another
298 manual to replace it.
300 Please spread the word about this issue. Our community continues to
301 lose manuals to proprietary publishing. If we spread the word that
302 free software needs free reference manuals and free tutorials, perhaps
303 the next person who wants to contribute by writing documentation will
304 realize, before it is too late, that only free manuals contribute to
305 the free software community.
307 If you are writing documentation, please insist on publishing it under
308 the GNU Free Documentation License or another free documentation
309 license. Remember that this decision requires your approval---you
310 don't have to let the publisher decide. Some commercial publishers
311 will use a free license if you insist, but they will not propose the
312 option; it is up to you to raise the issue and say firmly that this is
313 what you want. If the publisher you are dealing with refuses, please
314 try other publishers. If you're not sure whether a proposed license
315 is free, write to @email{licensing@@gnu.org}.
317 You can encourage commercial publishers to sell more free, copylefted
318 manuals and tutorials by buying them, and particularly by buying
319 copies from the publishers that paid for their writing or for major
320 improvements. Meanwhile, try to avoid buying non-free documentation
321 at all. Check the distribution terms of a manual before you buy it,
322 and insist that whoever seeks your business must respect your freedom.
323 Check the history of the book, and try to reward the publishers that
324 have paid or pay the authors to work on it.
326 The Free Software Foundation maintains a list of free documentation
327 published by other publishers, at
328 @url{http://www.fsf.org/doc/other-free-books.html}.
331 @unnumberedsec Contributors to @value{GDBN}
333 Richard Stallman was the original author of @value{GDBN}, and of many
334 other @sc{gnu} programs. Many others have contributed to its
335 development. This section attempts to credit major contributors. One
336 of the virtues of free software is that everyone is free to contribute
337 to it; with regret, we cannot actually acknowledge everyone here. The
338 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
339 blow-by-blow account.
341 Changes much prior to version 2.0 are lost in the mists of time.
344 @emph{Plea:} Additions to this section are particularly welcome. If you
345 or your friends (or enemies, to be evenhanded) have been unfairly
346 omitted from this list, we would like to add your names!
349 So that they may not regard their many labors as thankless, we
350 particularly thank those who shepherded @value{GDBN} through major
352 Andrew Cagney (releases 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
353 Jim Blandy (release 4.18);
354 Jason Molenda (release 4.17);
355 Stan Shebs (release 4.14);
356 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
357 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
358 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
359 Jim Kingdon (releases 3.5, 3.4, and 3.3);
360 and Randy Smith (releases 3.2, 3.1, and 3.0).
362 Richard Stallman, assisted at various times by Peter TerMaat, Chris
363 Hanson, and Richard Mlynarik, handled releases through 2.8.
365 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
366 in @value{GDBN}, with significant additional contributions from Per
367 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
368 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
369 much general update work leading to release 3.0).
371 @value{GDBN} uses the BFD subroutine library to examine multiple
372 object-file formats; BFD was a joint project of David V.
373 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
375 David Johnson wrote the original COFF support; Pace Willison did
376 the original support for encapsulated COFF.
378 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
380 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
381 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
383 Jean-Daniel Fekete contributed Sun 386i support.
384 Chris Hanson improved the HP9000 support.
385 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
386 David Johnson contributed Encore Umax support.
387 Jyrki Kuoppala contributed Altos 3068 support.
388 Jeff Law contributed HP PA and SOM support.
389 Keith Packard contributed NS32K support.
390 Doug Rabson contributed Acorn Risc Machine support.
391 Bob Rusk contributed Harris Nighthawk CX-UX support.
392 Chris Smith contributed Convex support (and Fortran debugging).
393 Jonathan Stone contributed Pyramid support.
394 Michael Tiemann contributed SPARC support.
395 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
396 Pace Willison contributed Intel 386 support.
397 Jay Vosburgh contributed Symmetry support.
398 Marko Mlinar contributed OpenRISC 1000 support.
400 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
402 Rich Schaefer and Peter Schauer helped with support of SunOS shared
405 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
406 about several machine instruction sets.
408 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
409 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
410 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
411 and RDI targets, respectively.
413 Brian Fox is the author of the readline libraries providing
414 command-line editing and command history.
416 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
417 Modula-2 support, and contributed the Languages chapter of this manual.
419 Fred Fish wrote most of the support for Unix System Vr4.
420 He also enhanced the command-completion support to cover C@t{++} overloaded
423 Hitachi America (now Renesas America), Ltd. sponsored the support for
424 H8/300, H8/500, and Super-H processors.
426 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
428 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
431 Toshiba sponsored the support for the TX39 Mips processor.
433 Matsushita sponsored the support for the MN10200 and MN10300 processors.
435 Fujitsu sponsored the support for SPARClite and FR30 processors.
437 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
440 Michael Snyder added support for tracepoints.
442 Stu Grossman wrote gdbserver.
444 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
445 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
447 The following people at the Hewlett-Packard Company contributed
448 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
449 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
450 compiler, and the Text User Interface (nee Terminal User Interface):
451 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
452 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
453 provided HP-specific information in this manual.
455 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
456 Robert Hoehne made significant contributions to the DJGPP port.
458 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
459 development since 1991. Cygnus engineers who have worked on @value{GDBN}
460 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
461 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
462 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
463 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
464 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
465 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
466 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
467 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
468 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
469 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
470 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
471 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
472 Zuhn have made contributions both large and small.
474 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
475 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
477 Jim Blandy added support for preprocessor macros, while working for Red
480 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
481 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
482 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
483 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
484 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
485 with the migration of old architectures to this new framework.
488 @chapter A Sample @value{GDBN} Session
490 You can use this manual at your leisure to read all about @value{GDBN}.
491 However, a handful of commands are enough to get started using the
492 debugger. This chapter illustrates those commands.
495 In this sample session, we emphasize user input like this: @b{input},
496 to make it easier to pick out from the surrounding output.
499 @c FIXME: this example may not be appropriate for some configs, where
500 @c FIXME...primary interest is in remote use.
502 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
503 processor) exhibits the following bug: sometimes, when we change its
504 quote strings from the default, the commands used to capture one macro
505 definition within another stop working. In the following short @code{m4}
506 session, we define a macro @code{foo} which expands to @code{0000}; we
507 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
508 same thing. However, when we change the open quote string to
509 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
510 procedure fails to define a new synonym @code{baz}:
519 @b{define(bar,defn(`foo'))}
523 @b{changequote(<QUOTE>,<UNQUOTE>)}
525 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
528 m4: End of input: 0: fatal error: EOF in string
532 Let us use @value{GDBN} to try to see what is going on.
535 $ @b{@value{GDBP} m4}
536 @c FIXME: this falsifies the exact text played out, to permit smallbook
537 @c FIXME... format to come out better.
538 @value{GDBN} is free software and you are welcome to distribute copies
539 of it under certain conditions; type "show copying" to see
541 There is absolutely no warranty for @value{GDBN}; type "show warranty"
544 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
549 @value{GDBN} reads only enough symbol data to know where to find the
550 rest when needed; as a result, the first prompt comes up very quickly.
551 We now tell @value{GDBN} to use a narrower display width than usual, so
552 that examples fit in this manual.
555 (@value{GDBP}) @b{set width 70}
559 We need to see how the @code{m4} built-in @code{changequote} works.
560 Having looked at the source, we know the relevant subroutine is
561 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
562 @code{break} command.
565 (@value{GDBP}) @b{break m4_changequote}
566 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
570 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
571 control; as long as control does not reach the @code{m4_changequote}
572 subroutine, the program runs as usual:
575 (@value{GDBP}) @b{run}
576 Starting program: /work/Editorial/gdb/gnu/m4/m4
584 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
585 suspends execution of @code{m4}, displaying information about the
586 context where it stops.
589 @b{changequote(<QUOTE>,<UNQUOTE>)}
591 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
593 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
597 Now we use the command @code{n} (@code{next}) to advance execution to
598 the next line of the current function.
602 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
607 @code{set_quotes} looks like a promising subroutine. We can go into it
608 by using the command @code{s} (@code{step}) instead of @code{next}.
609 @code{step} goes to the next line to be executed in @emph{any}
610 subroutine, so it steps into @code{set_quotes}.
614 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
616 530 if (lquote != def_lquote)
620 The display that shows the subroutine where @code{m4} is now
621 suspended (and its arguments) is called a stack frame display. It
622 shows a summary of the stack. We can use the @code{backtrace}
623 command (which can also be spelled @code{bt}), to see where we are
624 in the stack as a whole: the @code{backtrace} command displays a
625 stack frame for each active subroutine.
628 (@value{GDBP}) @b{bt}
629 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
631 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
633 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
634 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
636 #4 0x79dc in expand_input () at macro.c:40
637 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
641 We step through a few more lines to see what happens. The first two
642 times, we can use @samp{s}; the next two times we use @code{n} to avoid
643 falling into the @code{xstrdup} subroutine.
647 0x3b5c 532 if (rquote != def_rquote)
649 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
650 def_lquote : xstrdup(lq);
652 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
655 538 len_lquote = strlen(rquote);
659 The last line displayed looks a little odd; we can examine the variables
660 @code{lquote} and @code{rquote} to see if they are in fact the new left
661 and right quotes we specified. We use the command @code{p}
662 (@code{print}) to see their values.
665 (@value{GDBP}) @b{p lquote}
666 $1 = 0x35d40 "<QUOTE>"
667 (@value{GDBP}) @b{p rquote}
668 $2 = 0x35d50 "<UNQUOTE>"
672 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
673 To look at some context, we can display ten lines of source
674 surrounding the current line with the @code{l} (@code{list}) command.
680 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
682 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
685 538 len_lquote = strlen(rquote);
686 539 len_rquote = strlen(lquote);
693 Let us step past the two lines that set @code{len_lquote} and
694 @code{len_rquote}, and then examine the values of those variables.
698 539 len_rquote = strlen(lquote);
701 (@value{GDBP}) @b{p len_lquote}
703 (@value{GDBP}) @b{p len_rquote}
708 That certainly looks wrong, assuming @code{len_lquote} and
709 @code{len_rquote} are meant to be the lengths of @code{lquote} and
710 @code{rquote} respectively. We can set them to better values using
711 the @code{p} command, since it can print the value of
712 any expression---and that expression can include subroutine calls and
716 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
718 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
723 Is that enough to fix the problem of using the new quotes with the
724 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
725 executing with the @code{c} (@code{continue}) command, and then try the
726 example that caused trouble initially:
732 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
739 Success! The new quotes now work just as well as the default ones. The
740 problem seems to have been just the two typos defining the wrong
741 lengths. We allow @code{m4} exit by giving it an EOF as input:
745 Program exited normally.
749 The message @samp{Program exited normally.} is from @value{GDBN}; it
750 indicates @code{m4} has finished executing. We can end our @value{GDBN}
751 session with the @value{GDBN} @code{quit} command.
754 (@value{GDBP}) @b{quit}
758 @chapter Getting In and Out of @value{GDBN}
760 This chapter discusses how to start @value{GDBN}, and how to get out of it.
764 type @samp{@value{GDBP}} to start @value{GDBN}.
766 type @kbd{quit} or @kbd{C-d} to exit.
770 * Invoking GDB:: How to start @value{GDBN}
771 * Quitting GDB:: How to quit @value{GDBN}
772 * Shell Commands:: How to use shell commands inside @value{GDBN}
773 * Logging output:: How to log @value{GDBN}'s output to a file
777 @section Invoking @value{GDBN}
779 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
780 @value{GDBN} reads commands from the terminal until you tell it to exit.
782 You can also run @code{@value{GDBP}} with a variety of arguments and options,
783 to specify more of your debugging environment at the outset.
785 The command-line options described here are designed
786 to cover a variety of situations; in some environments, some of these
787 options may effectively be unavailable.
789 The most usual way to start @value{GDBN} is with one argument,
790 specifying an executable program:
793 @value{GDBP} @var{program}
797 You can also start with both an executable program and a core file
801 @value{GDBP} @var{program} @var{core}
804 You can, instead, specify a process ID as a second argument, if you want
805 to debug a running process:
808 @value{GDBP} @var{program} 1234
812 would attach @value{GDBN} to process @code{1234} (unless you also have a file
813 named @file{1234}; @value{GDBN} does check for a core file first).
815 Taking advantage of the second command-line argument requires a fairly
816 complete operating system; when you use @value{GDBN} as a remote
817 debugger attached to a bare board, there may not be any notion of
818 ``process'', and there is often no way to get a core dump. @value{GDBN}
819 will warn you if it is unable to attach or to read core dumps.
821 You can optionally have @code{@value{GDBP}} pass any arguments after the
822 executable file to the inferior using @code{--args}. This option stops
825 gdb --args gcc -O2 -c foo.c
827 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
828 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
830 You can run @code{@value{GDBP}} without printing the front material, which describes
831 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
838 You can further control how @value{GDBN} starts up by using command-line
839 options. @value{GDBN} itself can remind you of the options available.
849 to display all available options and briefly describe their use
850 (@samp{@value{GDBP} -h} is a shorter equivalent).
852 All options and command line arguments you give are processed
853 in sequential order. The order makes a difference when the
854 @samp{-x} option is used.
858 * File Options:: Choosing files
859 * Mode Options:: Choosing modes
860 * Startup:: What @value{GDBN} does during startup
864 @subsection Choosing files
866 When @value{GDBN} starts, it reads any arguments other than options as
867 specifying an executable file and core file (or process ID). This is
868 the same as if the arguments were specified by the @samp{-se} and
869 @samp{-c} (or @samp{-p} options respectively. (@value{GDBN} reads the
870 first argument that does not have an associated option flag as
871 equivalent to the @samp{-se} option followed by that argument; and the
872 second argument that does not have an associated option flag, if any, as
873 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
874 If the second argument begins with a decimal digit, @value{GDBN} will
875 first attempt to attach to it as a process, and if that fails, attempt
876 to open it as a corefile. If you have a corefile whose name begins with
877 a digit, you can prevent @value{GDBN} from treating it as a pid by
878 prefixing it with @file{./}, eg. @file{./12345}.
880 If @value{GDBN} has not been configured to included core file support,
881 such as for most embedded targets, then it will complain about a second
882 argument and ignore it.
884 Many options have both long and short forms; both are shown in the
885 following list. @value{GDBN} also recognizes the long forms if you truncate
886 them, so long as enough of the option is present to be unambiguous.
887 (If you prefer, you can flag option arguments with @samp{--} rather
888 than @samp{-}, though we illustrate the more usual convention.)
890 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
891 @c way, both those who look for -foo and --foo in the index, will find
895 @item -symbols @var{file}
897 @cindex @code{--symbols}
899 Read symbol table from file @var{file}.
901 @item -exec @var{file}
903 @cindex @code{--exec}
905 Use file @var{file} as the executable file to execute when appropriate,
906 and for examining pure data in conjunction with a core dump.
910 Read symbol table from file @var{file} and use it as the executable
913 @item -core @var{file}
915 @cindex @code{--core}
917 Use file @var{file} as a core dump to examine.
919 @item -c @var{number}
920 @item -pid @var{number}
921 @itemx -p @var{number}
924 Connect to process ID @var{number}, as with the @code{attach} command.
925 If there is no such process, @value{GDBN} will attempt to open a core
926 file named @var{number}.
928 @item -command @var{file}
930 @cindex @code{--command}
932 Execute @value{GDBN} commands from file @var{file}. @xref{Command
933 Files,, Command files}.
935 @item -directory @var{directory}
936 @itemx -d @var{directory}
937 @cindex @code{--directory}
939 Add @var{directory} to the path to search for source files.
943 @cindex @code{--mapped}
945 @emph{Warning: this option depends on operating system facilities that are not
946 supported on all systems.}@*
947 If memory-mapped files are available on your system through the @code{mmap}
948 system call, you can use this option
949 to have @value{GDBN} write the symbols from your
950 program into a reusable file in the current directory. If the program you are debugging is
951 called @file{/tmp/fred}, the mapped symbol file is @file{/tmp/fred.syms}.
952 Future @value{GDBN} debugging sessions notice the presence of this file,
953 and can quickly map in symbol information from it, rather than reading
954 the symbol table from the executable program.
956 The @file{.syms} file is specific to the host machine where @value{GDBN}
957 is run. It holds an exact image of the internal @value{GDBN} symbol
958 table. It cannot be shared across multiple host platforms.
962 @cindex @code{--readnow}
964 Read each symbol file's entire symbol table immediately, rather than
965 the default, which is to read it incrementally as it is needed.
966 This makes startup slower, but makes future operations faster.
970 You typically combine the @code{-mapped} and @code{-readnow} options in
971 order to build a @file{.syms} file that contains complete symbol
972 information. (@xref{Files,,Commands to specify files}, for information
973 on @file{.syms} files.) A simple @value{GDBN} invocation to do nothing
974 but build a @file{.syms} file for future use is:
977 gdb -batch -nx -mapped -readnow programname
981 @subsection Choosing modes
983 You can run @value{GDBN} in various alternative modes---for example, in
984 batch mode or quiet mode.
991 Do not execute commands found in any initialization files. Normally,
992 @value{GDBN} executes the commands in these files after all the command
993 options and arguments have been processed. @xref{Command Files,,Command
999 @cindex @code{--quiet}
1000 @cindex @code{--silent}
1002 ``Quiet''. Do not print the introductory and copyright messages. These
1003 messages are also suppressed in batch mode.
1006 @cindex @code{--batch}
1007 Run in batch mode. Exit with status @code{0} after processing all the
1008 command files specified with @samp{-x} (and all commands from
1009 initialization files, if not inhibited with @samp{-n}). Exit with
1010 nonzero status if an error occurs in executing the @value{GDBN} commands
1011 in the command files.
1013 Batch mode may be useful for running @value{GDBN} as a filter, for
1014 example to download and run a program on another computer; in order to
1015 make this more useful, the message
1018 Program exited normally.
1022 (which is ordinarily issued whenever a program running under
1023 @value{GDBN} control terminates) is not issued when running in batch
1028 @cindex @code{--nowindows}
1030 ``No windows''. If @value{GDBN} comes with a graphical user interface
1031 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1032 interface. If no GUI is available, this option has no effect.
1036 @cindex @code{--windows}
1038 If @value{GDBN} includes a GUI, then this option requires it to be
1041 @item -cd @var{directory}
1043 Run @value{GDBN} using @var{directory} as its working directory,
1044 instead of the current directory.
1048 @cindex @code{--fullname}
1050 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1051 subprocess. It tells @value{GDBN} to output the full file name and line
1052 number in a standard, recognizable fashion each time a stack frame is
1053 displayed (which includes each time your program stops). This
1054 recognizable format looks like two @samp{\032} characters, followed by
1055 the file name, line number and character position separated by colons,
1056 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1057 @samp{\032} characters as a signal to display the source code for the
1061 @cindex @code{--epoch}
1062 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1063 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1064 routines so as to allow Epoch to display values of expressions in a
1067 @item -annotate @var{level}
1068 @cindex @code{--annotate}
1069 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1070 effect is identical to using @samp{set annotate @var{level}}
1071 (@pxref{Annotations}). The annotation @var{level} controls how much
1072 information @value{GDBN} prints together with its prompt, values of
1073 expressions, source lines, and other types of output. Level 0 is the
1074 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1075 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1076 that control @value{GDBN}, and level 2 has been deprecated.
1078 The annotation mechanism has largely been superseeded by @sc{gdb/mi}
1082 @cindex @code{--args}
1083 Change interpretation of command line so that arguments following the
1084 executable file are passed as command line arguments to the inferior.
1085 This option stops option processing.
1087 @item -baud @var{bps}
1089 @cindex @code{--baud}
1091 Set the line speed (baud rate or bits per second) of any serial
1092 interface used by @value{GDBN} for remote debugging.
1094 @item -l @var{timeout}
1096 Set the timeout (in seconds) of any communication used by @value{GDBN}
1097 for remote debugging.
1099 @item -tty @var{device}
1100 @itemx -t @var{device}
1101 @cindex @code{--tty}
1103 Run using @var{device} for your program's standard input and output.
1104 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1106 @c resolve the situation of these eventually
1108 @cindex @code{--tui}
1109 Activate the @dfn{Text User Interface} when starting. The Text User
1110 Interface manages several text windows on the terminal, showing
1111 source, assembly, registers and @value{GDBN} command outputs
1112 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1113 Text User Interface can be enabled by invoking the program
1114 @samp{gdbtui}. Do not use this option if you run @value{GDBN} from
1115 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1118 @c @cindex @code{--xdb}
1119 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1120 @c For information, see the file @file{xdb_trans.html}, which is usually
1121 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1124 @item -interpreter @var{interp}
1125 @cindex @code{--interpreter}
1126 Use the interpreter @var{interp} for interface with the controlling
1127 program or device. This option is meant to be set by programs which
1128 communicate with @value{GDBN} using it as a back end.
1129 @xref{Interpreters, , Command Interpreters}.
1131 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1132 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1133 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1134 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1135 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1136 @sc{gdb/mi} interfaces are no longer supported.
1139 @cindex @code{--write}
1140 Open the executable and core files for both reading and writing. This
1141 is equivalent to the @samp{set write on} command inside @value{GDBN}
1145 @cindex @code{--statistics}
1146 This option causes @value{GDBN} to print statistics about time and
1147 memory usage after it completes each command and returns to the prompt.
1150 @cindex @code{--version}
1151 This option causes @value{GDBN} to print its version number and
1152 no-warranty blurb, and exit.
1157 @subsection What @value{GDBN} does during startup
1158 @cindex @value{GDBN} startup
1160 Here's the description of what @value{GDBN} does during session startup:
1164 Sets up the command interpreter as specified by the command line
1165 (@pxref{Mode Options, interpreter}).
1169 Reads the @dfn{init file} (if any) in your home directory@footnote{On
1170 DOS/Windows systems, the home directory is the one pointed to by the
1171 @code{HOME} environment variable.} and executes all the commands in
1175 Processes command line options and operands.
1178 Reads and executes the commands from init file (if any) in the current
1179 working directory. This is only done if the current directory is
1180 different from your home directory. Thus, you can have more than one
1181 init file, one generic in your home directory, and another, specific
1182 to the program you are debugging, in the directory where you invoke
1186 Reads command files specified by the @samp{-x} option. @xref{Command
1187 Files}, for more details about @value{GDBN} command files.
1190 Reads the command history recorded in the @dfn{history file}.
1191 @xref{History}, for more details about the command history and the
1192 files where @value{GDBN} records it.
1195 Init files use the same syntax as @dfn{command files} (@pxref{Command
1196 Files}) and are processed by @value{GDBN} in the same way. The init
1197 file in your home directory can set options (such as @samp{set
1198 complaints}) that affect subsequent processing of command line options
1199 and operands. Init files are not executed if you use the @samp{-nx}
1200 option (@pxref{Mode Options, ,Choosing modes}).
1202 @cindex init file name
1203 @cindex @file{.gdbinit}
1204 The @value{GDBN} init files are normally called @file{.gdbinit}.
1205 On some configurations of @value{GDBN}, the init file is known by a
1206 different name (these are typically environments where a specialized
1207 form of @value{GDBN} may need to coexist with other forms, hence a
1208 different name for the specialized version's init file). These are the
1209 environments with special init file names:
1212 @cindex @file{gdb.ini}
1214 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1215 the limitations of file names imposed by DOS filesystems. The Windows
1216 ports of @value{GDBN} use the standard name, but if they find a
1217 @file{gdb.ini} file, they warn you about that and suggest to rename
1218 the file to the standard name.
1220 @cindex @file{.vxgdbinit}
1222 VxWorks (Wind River Systems real-time OS): @file{.vxgdbinit}
1224 @cindex @file{.os68gdbinit}
1226 OS68K (Enea Data Systems real-time OS): @file{.os68gdbinit}
1228 @cindex @file{.esgdbinit}
1230 ES-1800 (Ericsson Telecom AB M68000 emulator): @file{.esgdbinit}
1233 CISCO 68k: @file{.cisco-gdbinit}
1238 @section Quitting @value{GDBN}
1239 @cindex exiting @value{GDBN}
1240 @cindex leaving @value{GDBN}
1243 @kindex quit @r{[}@var{expression}@r{]}
1244 @kindex q @r{(@code{quit})}
1245 @item quit @r{[}@var{expression}@r{]}
1247 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1248 @code{q}), or type an end-of-file character (usually @kbd{C-d}). If you
1249 do not supply @var{expression}, @value{GDBN} will terminate normally;
1250 otherwise it will terminate using the result of @var{expression} as the
1255 An interrupt (often @kbd{C-c}) does not exit from @value{GDBN}, but rather
1256 terminates the action of any @value{GDBN} command that is in progress and
1257 returns to @value{GDBN} command level. It is safe to type the interrupt
1258 character at any time because @value{GDBN} does not allow it to take effect
1259 until a time when it is safe.
1261 If you have been using @value{GDBN} to control an attached process or
1262 device, you can release it with the @code{detach} command
1263 (@pxref{Attach, ,Debugging an already-running process}).
1265 @node Shell Commands
1266 @section Shell commands
1268 If you need to execute occasional shell commands during your
1269 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1270 just use the @code{shell} command.
1274 @cindex shell escape
1275 @item shell @var{command string}
1276 Invoke a standard shell to execute @var{command string}.
1277 If it exists, the environment variable @code{SHELL} determines which
1278 shell to run. Otherwise @value{GDBN} uses the default shell
1279 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1282 The utility @code{make} is often needed in development environments.
1283 You do not have to use the @code{shell} command for this purpose in
1288 @cindex calling make
1289 @item make @var{make-args}
1290 Execute the @code{make} program with the specified
1291 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1294 @node Logging output
1295 @section Logging output
1296 @cindex logging @value{GDBN} output
1297 @cindex save @value{GDBN} output to a file
1299 You may want to save the output of @value{GDBN} commands to a file.
1300 There are several commands to control @value{GDBN}'s logging.
1304 @item set logging on
1306 @item set logging off
1308 @cindex logging file name
1309 @item set logging file @var{file}
1310 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1311 @item set logging overwrite [on|off]
1312 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1313 you want @code{set logging on} to overwrite the logfile instead.
1314 @item set logging redirect [on|off]
1315 By default, @value{GDBN} output will go to both the terminal and the logfile.
1316 Set @code{redirect} if you want output to go only to the log file.
1317 @kindex show logging
1319 Show the current values of the logging settings.
1323 @chapter @value{GDBN} Commands
1325 You can abbreviate a @value{GDBN} command to the first few letters of the command
1326 name, if that abbreviation is unambiguous; and you can repeat certain
1327 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1328 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1329 show you the alternatives available, if there is more than one possibility).
1332 * Command Syntax:: How to give commands to @value{GDBN}
1333 * Completion:: Command completion
1334 * Help:: How to ask @value{GDBN} for help
1337 @node Command Syntax
1338 @section Command syntax
1340 A @value{GDBN} command is a single line of input. There is no limit on
1341 how long it can be. It starts with a command name, which is followed by
1342 arguments whose meaning depends on the command name. For example, the
1343 command @code{step} accepts an argument which is the number of times to
1344 step, as in @samp{step 5}. You can also use the @code{step} command
1345 with no arguments. Some commands do not allow any arguments.
1347 @cindex abbreviation
1348 @value{GDBN} command names may always be truncated if that abbreviation is
1349 unambiguous. Other possible command abbreviations are listed in the
1350 documentation for individual commands. In some cases, even ambiguous
1351 abbreviations are allowed; for example, @code{s} is specially defined as
1352 equivalent to @code{step} even though there are other commands whose
1353 names start with @code{s}. You can test abbreviations by using them as
1354 arguments to the @code{help} command.
1356 @cindex repeating commands
1357 @kindex RET @r{(repeat last command)}
1358 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1359 repeat the previous command. Certain commands (for example, @code{run})
1360 will not repeat this way; these are commands whose unintentional
1361 repetition might cause trouble and which you are unlikely to want to
1362 repeat. User-defined commands can disable this feature; see
1363 @ref{Define, dont-repeat}.
1365 The @code{list} and @code{x} commands, when you repeat them with
1366 @key{RET}, construct new arguments rather than repeating
1367 exactly as typed. This permits easy scanning of source or memory.
1369 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1370 output, in a way similar to the common utility @code{more}
1371 (@pxref{Screen Size,,Screen size}). Since it is easy to press one
1372 @key{RET} too many in this situation, @value{GDBN} disables command
1373 repetition after any command that generates this sort of display.
1375 @kindex # @r{(a comment)}
1377 Any text from a @kbd{#} to the end of the line is a comment; it does
1378 nothing. This is useful mainly in command files (@pxref{Command
1379 Files,,Command files}).
1381 @cindex repeating command sequences
1382 @kindex C-o @r{(operate-and-get-next)}
1383 The @kbd{C-o} binding is useful for repeating a complex sequence of
1384 commands. This command accepts the current line, like @kbd{RET}, and
1385 then fetches the next line relative to the current line from the history
1389 @section Command completion
1392 @cindex word completion
1393 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1394 only one possibility; it can also show you what the valid possibilities
1395 are for the next word in a command, at any time. This works for @value{GDBN}
1396 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1398 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1399 of a word. If there is only one possibility, @value{GDBN} fills in the
1400 word, and waits for you to finish the command (or press @key{RET} to
1401 enter it). For example, if you type
1403 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1404 @c complete accuracy in these examples; space introduced for clarity.
1405 @c If texinfo enhancements make it unnecessary, it would be nice to
1406 @c replace " @key" by "@key" in the following...
1408 (@value{GDBP}) info bre @key{TAB}
1412 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1413 the only @code{info} subcommand beginning with @samp{bre}:
1416 (@value{GDBP}) info breakpoints
1420 You can either press @key{RET} at this point, to run the @code{info
1421 breakpoints} command, or backspace and enter something else, if
1422 @samp{breakpoints} does not look like the command you expected. (If you
1423 were sure you wanted @code{info breakpoints} in the first place, you
1424 might as well just type @key{RET} immediately after @samp{info bre},
1425 to exploit command abbreviations rather than command completion).
1427 If there is more than one possibility for the next word when you press
1428 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1429 characters and try again, or just press @key{TAB} a second time;
1430 @value{GDBN} displays all the possible completions for that word. For
1431 example, you might want to set a breakpoint on a subroutine whose name
1432 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1433 just sounds the bell. Typing @key{TAB} again displays all the
1434 function names in your program that begin with those characters, for
1438 (@value{GDBP}) b make_ @key{TAB}
1439 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1440 make_a_section_from_file make_environ
1441 make_abs_section make_function_type
1442 make_blockvector make_pointer_type
1443 make_cleanup make_reference_type
1444 make_command make_symbol_completion_list
1445 (@value{GDBP}) b make_
1449 After displaying the available possibilities, @value{GDBN} copies your
1450 partial input (@samp{b make_} in the example) so you can finish the
1453 If you just want to see the list of alternatives in the first place, you
1454 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1455 means @kbd{@key{META} ?}. You can type this either by holding down a
1456 key designated as the @key{META} shift on your keyboard (if there is
1457 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1459 @cindex quotes in commands
1460 @cindex completion of quoted strings
1461 Sometimes the string you need, while logically a ``word'', may contain
1462 parentheses or other characters that @value{GDBN} normally excludes from
1463 its notion of a word. To permit word completion to work in this
1464 situation, you may enclose words in @code{'} (single quote marks) in
1465 @value{GDBN} commands.
1467 The most likely situation where you might need this is in typing the
1468 name of a C@t{++} function. This is because C@t{++} allows function
1469 overloading (multiple definitions of the same function, distinguished
1470 by argument type). For example, when you want to set a breakpoint you
1471 may need to distinguish whether you mean the version of @code{name}
1472 that takes an @code{int} parameter, @code{name(int)}, or the version
1473 that takes a @code{float} parameter, @code{name(float)}. To use the
1474 word-completion facilities in this situation, type a single quote
1475 @code{'} at the beginning of the function name. This alerts
1476 @value{GDBN} that it may need to consider more information than usual
1477 when you press @key{TAB} or @kbd{M-?} to request word completion:
1480 (@value{GDBP}) b 'bubble( @kbd{M-?}
1481 bubble(double,double) bubble(int,int)
1482 (@value{GDBP}) b 'bubble(
1485 In some cases, @value{GDBN} can tell that completing a name requires using
1486 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1487 completing as much as it can) if you do not type the quote in the first
1491 (@value{GDBP}) b bub @key{TAB}
1492 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1493 (@value{GDBP}) b 'bubble(
1497 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1498 you have not yet started typing the argument list when you ask for
1499 completion on an overloaded symbol.
1501 For more information about overloaded functions, see @ref{C plus plus
1502 expressions, ,C@t{++} expressions}. You can use the command @code{set
1503 overload-resolution off} to disable overload resolution;
1504 see @ref{Debugging C plus plus, ,@value{GDBN} features for C@t{++}}.
1508 @section Getting help
1509 @cindex online documentation
1512 You can always ask @value{GDBN} itself for information on its commands,
1513 using the command @code{help}.
1516 @kindex h @r{(@code{help})}
1519 You can use @code{help} (abbreviated @code{h}) with no arguments to
1520 display a short list of named classes of commands:
1524 List of classes of commands:
1526 aliases -- Aliases of other commands
1527 breakpoints -- Making program stop at certain points
1528 data -- Examining data
1529 files -- Specifying and examining files
1530 internals -- Maintenance commands
1531 obscure -- Obscure features
1532 running -- Running the program
1533 stack -- Examining the stack
1534 status -- Status inquiries
1535 support -- Support facilities
1536 tracepoints -- Tracing of program execution without@*
1537 stopping the program
1538 user-defined -- User-defined commands
1540 Type "help" followed by a class name for a list of
1541 commands in that class.
1542 Type "help" followed by command name for full
1544 Command name abbreviations are allowed if unambiguous.
1547 @c the above line break eliminates huge line overfull...
1549 @item help @var{class}
1550 Using one of the general help classes as an argument, you can get a
1551 list of the individual commands in that class. For example, here is the
1552 help display for the class @code{status}:
1555 (@value{GDBP}) help status
1560 @c Line break in "show" line falsifies real output, but needed
1561 @c to fit in smallbook page size.
1562 info -- Generic command for showing things
1563 about the program being debugged
1564 show -- Generic command for showing things
1567 Type "help" followed by command name for full
1569 Command name abbreviations are allowed if unambiguous.
1573 @item help @var{command}
1574 With a command name as @code{help} argument, @value{GDBN} displays a
1575 short paragraph on how to use that command.
1578 @item apropos @var{args}
1579 The @code{apropos} command searches through all of the @value{GDBN}
1580 commands, and their documentation, for the regular expression specified in
1581 @var{args}. It prints out all matches found. For example:
1592 set symbol-reloading -- Set dynamic symbol table reloading
1593 multiple times in one run
1594 show symbol-reloading -- Show dynamic symbol table reloading
1595 multiple times in one run
1600 @item complete @var{args}
1601 The @code{complete @var{args}} command lists all the possible completions
1602 for the beginning of a command. Use @var{args} to specify the beginning of the
1603 command you want completed. For example:
1609 @noindent results in:
1620 @noindent This is intended for use by @sc{gnu} Emacs.
1623 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1624 and @code{show} to inquire about the state of your program, or the state
1625 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1626 manual introduces each of them in the appropriate context. The listings
1627 under @code{info} and under @code{show} in the Index point to
1628 all the sub-commands. @xref{Index}.
1633 @kindex i @r{(@code{info})}
1635 This command (abbreviated @code{i}) is for describing the state of your
1636 program. For example, you can list the arguments given to your program
1637 with @code{info args}, list the registers currently in use with @code{info
1638 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1639 You can get a complete list of the @code{info} sub-commands with
1640 @w{@code{help info}}.
1644 You can assign the result of an expression to an environment variable with
1645 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1646 @code{set prompt $}.
1650 In contrast to @code{info}, @code{show} is for describing the state of
1651 @value{GDBN} itself.
1652 You can change most of the things you can @code{show}, by using the
1653 related command @code{set}; for example, you can control what number
1654 system is used for displays with @code{set radix}, or simply inquire
1655 which is currently in use with @code{show radix}.
1658 To display all the settable parameters and their current
1659 values, you can use @code{show} with no arguments; you may also use
1660 @code{info set}. Both commands produce the same display.
1661 @c FIXME: "info set" violates the rule that "info" is for state of
1662 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1663 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1667 Here are three miscellaneous @code{show} subcommands, all of which are
1668 exceptional in lacking corresponding @code{set} commands:
1671 @kindex show version
1672 @cindex @value{GDBN} version number
1674 Show what version of @value{GDBN} is running. You should include this
1675 information in @value{GDBN} bug-reports. If multiple versions of
1676 @value{GDBN} are in use at your site, you may need to determine which
1677 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1678 commands are introduced, and old ones may wither away. Also, many
1679 system vendors ship variant versions of @value{GDBN}, and there are
1680 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1681 The version number is the same as the one announced when you start
1684 @kindex show copying
1685 @kindex info copying
1686 @cindex display @value{GDBN} copyright
1689 Display information about permission for copying @value{GDBN}.
1691 @kindex show warranty
1692 @kindex info warranty
1694 @itemx info warranty
1695 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1696 if your version of @value{GDBN} comes with one.
1701 @chapter Running Programs Under @value{GDBN}
1703 When you run a program under @value{GDBN}, you must first generate
1704 debugging information when you compile it.
1706 You may start @value{GDBN} with its arguments, if any, in an environment
1707 of your choice. If you are doing native debugging, you may redirect
1708 your program's input and output, debug an already running process, or
1709 kill a child process.
1712 * Compilation:: Compiling for debugging
1713 * Starting:: Starting your program
1714 * Arguments:: Your program's arguments
1715 * Environment:: Your program's environment
1717 * Working Directory:: Your program's working directory
1718 * Input/Output:: Your program's input and output
1719 * Attach:: Debugging an already-running process
1720 * Kill Process:: Killing the child process
1722 * Threads:: Debugging programs with multiple threads
1723 * Processes:: Debugging programs with multiple processes
1727 @section Compiling for debugging
1729 In order to debug a program effectively, you need to generate
1730 debugging information when you compile it. This debugging information
1731 is stored in the object file; it describes the data type of each
1732 variable or function and the correspondence between source line numbers
1733 and addresses in the executable code.
1735 To request debugging information, specify the @samp{-g} option when you run
1738 Programs that are to be shipped to your customers are compiled with
1739 optimizations, using the @samp{-O} compiler option. However, many
1740 compilers are unable to handle the @samp{-g} and @samp{-O} options
1741 together. Using those compilers, you cannot generate optimized
1742 executables containing debugging information.
1744 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1745 without @samp{-O}, making it possible to debug optimized code. We
1746 recommend that you @emph{always} use @samp{-g} whenever you compile a
1747 program. You may think your program is correct, but there is no sense
1748 in pushing your luck.
1750 @cindex optimized code, debugging
1751 @cindex debugging optimized code
1752 When you debug a program compiled with @samp{-g -O}, remember that the
1753 optimizer is rearranging your code; the debugger shows you what is
1754 really there. Do not be too surprised when the execution path does not
1755 exactly match your source file! An extreme example: if you define a
1756 variable, but never use it, @value{GDBN} never sees that
1757 variable---because the compiler optimizes it out of existence.
1759 Some things do not work as well with @samp{-g -O} as with just
1760 @samp{-g}, particularly on machines with instruction scheduling. If in
1761 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1762 please report it to us as a bug (including a test case!).
1763 @xref{Variables}, for more information about debugging optimized code.
1765 Older versions of the @sc{gnu} C compiler permitted a variant option
1766 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1767 format; if your @sc{gnu} C compiler has this option, do not use it.
1769 @value{GDBN} knows about preprocessor macros and can show you their
1770 expansion (@pxref{Macros}). Most compilers do not include information
1771 about preprocessor macros in the debugging information if you specify
1772 the @option{-g} flag alone, because this information is rather large.
1773 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1774 provides macro information if you specify the options
1775 @option{-gdwarf-2} and @option{-g3}; the former option requests
1776 debugging information in the Dwarf 2 format, and the latter requests
1777 ``extra information''. In the future, we hope to find more compact
1778 ways to represent macro information, so that it can be included with
1783 @section Starting your program
1789 @kindex r @r{(@code{run})}
1792 Use the @code{run} command to start your program under @value{GDBN}.
1793 You must first specify the program name (except on VxWorks) with an
1794 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1795 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1796 (@pxref{Files, ,Commands to specify files}).
1800 If you are running your program in an execution environment that
1801 supports processes, @code{run} creates an inferior process and makes
1802 that process run your program. (In environments without processes,
1803 @code{run} jumps to the start of your program.)
1805 The execution of a program is affected by certain information it
1806 receives from its superior. @value{GDBN} provides ways to specify this
1807 information, which you must do @emph{before} starting your program. (You
1808 can change it after starting your program, but such changes only affect
1809 your program the next time you start it.) This information may be
1810 divided into four categories:
1813 @item The @emph{arguments.}
1814 Specify the arguments to give your program as the arguments of the
1815 @code{run} command. If a shell is available on your target, the shell
1816 is used to pass the arguments, so that you may use normal conventions
1817 (such as wildcard expansion or variable substitution) in describing
1819 In Unix systems, you can control which shell is used with the
1820 @code{SHELL} environment variable.
1821 @xref{Arguments, ,Your program's arguments}.
1823 @item The @emph{environment.}
1824 Your program normally inherits its environment from @value{GDBN}, but you can
1825 use the @value{GDBN} commands @code{set environment} and @code{unset
1826 environment} to change parts of the environment that affect
1827 your program. @xref{Environment, ,Your program's environment}.
1829 @item The @emph{working directory.}
1830 Your program inherits its working directory from @value{GDBN}. You can set
1831 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1832 @xref{Working Directory, ,Your program's working directory}.
1834 @item The @emph{standard input and output.}
1835 Your program normally uses the same device for standard input and
1836 standard output as @value{GDBN} is using. You can redirect input and output
1837 in the @code{run} command line, or you can use the @code{tty} command to
1838 set a different device for your program.
1839 @xref{Input/Output, ,Your program's input and output}.
1842 @emph{Warning:} While input and output redirection work, you cannot use
1843 pipes to pass the output of the program you are debugging to another
1844 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1848 When you issue the @code{run} command, your program begins to execute
1849 immediately. @xref{Stopping, ,Stopping and continuing}, for discussion
1850 of how to arrange for your program to stop. Once your program has
1851 stopped, you may call functions in your program, using the @code{print}
1852 or @code{call} commands. @xref{Data, ,Examining Data}.
1854 If the modification time of your symbol file has changed since the last
1855 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1856 table, and reads it again. When it does this, @value{GDBN} tries to retain
1857 your current breakpoints.
1862 @cindex run to main procedure
1863 The name of the main procedure can vary from language to language.
1864 With C or C@t{++}, the main procedure name is always @code{main}, but
1865 other languages such as Ada do not require a specific name for their
1866 main procedure. The debugger provides a convenient way to start the
1867 execution of the program and to stop at the beginning of the main
1868 procedure, depending on the language used.
1870 The @samp{start} command does the equivalent of setting a temporary
1871 breakpoint at the beginning of the main procedure and then invoking
1872 the @samp{run} command.
1874 @cindex elaboration phase
1875 Some programs contain an @dfn{elaboration} phase where some startup code is
1876 executed before the main procedure is called. This depends on the
1877 languages used to write your program. In C@t{++}, for instance,
1878 constructors for static and global objects are executed before
1879 @code{main} is called. It is therefore possible that the debugger stops
1880 before reaching the main procedure. However, the temporary breakpoint
1881 will remain to halt execution.
1883 Specify the arguments to give to your program as arguments to the
1884 @samp{start} command. These arguments will be given verbatim to the
1885 underlying @samp{run} command. Note that the same arguments will be
1886 reused if no argument is provided during subsequent calls to
1887 @samp{start} or @samp{run}.
1889 It is sometimes necessary to debug the program during elaboration. In
1890 these cases, using the @code{start} command would stop the execution of
1891 your program too late, as the program would have already completed the
1892 elaboration phase. Under these circumstances, insert breakpoints in your
1893 elaboration code before running your program.
1897 @section Your program's arguments
1899 @cindex arguments (to your program)
1900 The arguments to your program can be specified by the arguments of the
1902 They are passed to a shell, which expands wildcard characters and
1903 performs redirection of I/O, and thence to your program. Your
1904 @code{SHELL} environment variable (if it exists) specifies what shell
1905 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1906 the default shell (@file{/bin/sh} on Unix).
1908 On non-Unix systems, the program is usually invoked directly by
1909 @value{GDBN}, which emulates I/O redirection via the appropriate system
1910 calls, and the wildcard characters are expanded by the startup code of
1911 the program, not by the shell.
1913 @code{run} with no arguments uses the same arguments used by the previous
1914 @code{run}, or those set by the @code{set args} command.
1919 Specify the arguments to be used the next time your program is run. If
1920 @code{set args} has no arguments, @code{run} executes your program
1921 with no arguments. Once you have run your program with arguments,
1922 using @code{set args} before the next @code{run} is the only way to run
1923 it again without arguments.
1927 Show the arguments to give your program when it is started.
1931 @section Your program's environment
1933 @cindex environment (of your program)
1934 The @dfn{environment} consists of a set of environment variables and
1935 their values. Environment variables conventionally record such things as
1936 your user name, your home directory, your terminal type, and your search
1937 path for programs to run. Usually you set up environment variables with
1938 the shell and they are inherited by all the other programs you run. When
1939 debugging, it can be useful to try running your program with a modified
1940 environment without having to start @value{GDBN} over again.
1944 @item path @var{directory}
1945 Add @var{directory} to the front of the @code{PATH} environment variable
1946 (the search path for executables) that will be passed to your program.
1947 The value of @code{PATH} used by @value{GDBN} does not change.
1948 You may specify several directory names, separated by whitespace or by a
1949 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1950 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1951 is moved to the front, so it is searched sooner.
1953 You can use the string @samp{$cwd} to refer to whatever is the current
1954 working directory at the time @value{GDBN} searches the path. If you
1955 use @samp{.} instead, it refers to the directory where you executed the
1956 @code{path} command. @value{GDBN} replaces @samp{.} in the
1957 @var{directory} argument (with the current path) before adding
1958 @var{directory} to the search path.
1959 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1960 @c document that, since repeating it would be a no-op.
1964 Display the list of search paths for executables (the @code{PATH}
1965 environment variable).
1967 @kindex show environment
1968 @item show environment @r{[}@var{varname}@r{]}
1969 Print the value of environment variable @var{varname} to be given to
1970 your program when it starts. If you do not supply @var{varname},
1971 print the names and values of all environment variables to be given to
1972 your program. You can abbreviate @code{environment} as @code{env}.
1974 @kindex set environment
1975 @item set environment @var{varname} @r{[}=@var{value}@r{]}
1976 Set environment variable @var{varname} to @var{value}. The value
1977 changes for your program only, not for @value{GDBN} itself. @var{value} may
1978 be any string; the values of environment variables are just strings, and
1979 any interpretation is supplied by your program itself. The @var{value}
1980 parameter is optional; if it is eliminated, the variable is set to a
1982 @c "any string" here does not include leading, trailing
1983 @c blanks. Gnu asks: does anyone care?
1985 For example, this command:
1992 tells the debugged program, when subsequently run, that its user is named
1993 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
1994 are not actually required.)
1996 @kindex unset environment
1997 @item unset environment @var{varname}
1998 Remove variable @var{varname} from the environment to be passed to your
1999 program. This is different from @samp{set env @var{varname} =};
2000 @code{unset environment} removes the variable from the environment,
2001 rather than assigning it an empty value.
2004 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2006 by your @code{SHELL} environment variable if it exists (or
2007 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2008 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2009 @file{.bashrc} for BASH---any variables you set in that file affect
2010 your program. You may wish to move setting of environment variables to
2011 files that are only run when you sign on, such as @file{.login} or
2014 @node Working Directory
2015 @section Your program's working directory
2017 @cindex working directory (of your program)
2018 Each time you start your program with @code{run}, it inherits its
2019 working directory from the current working directory of @value{GDBN}.
2020 The @value{GDBN} working directory is initially whatever it inherited
2021 from its parent process (typically the shell), but you can specify a new
2022 working directory in @value{GDBN} with the @code{cd} command.
2024 The @value{GDBN} working directory also serves as a default for the commands
2025 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2030 @cindex change working directory
2031 @item cd @var{directory}
2032 Set the @value{GDBN} working directory to @var{directory}.
2036 Print the @value{GDBN} working directory.
2039 It is generally impossible to find the current working directory of
2040 the process being debugged (since a program can change its directory
2041 during its run). If you work on a system where @value{GDBN} is
2042 configured with the @file{/proc} support, you can use the @code{info
2043 proc} command (@pxref{SVR4 Process Information}) to find out the
2044 current working directory of the debuggee.
2047 @section Your program's input and output
2052 By default, the program you run under @value{GDBN} does input and output to
2053 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2054 to its own terminal modes to interact with you, but it records the terminal
2055 modes your program was using and switches back to them when you continue
2056 running your program.
2059 @kindex info terminal
2061 Displays information recorded by @value{GDBN} about the terminal modes your
2065 You can redirect your program's input and/or output using shell
2066 redirection with the @code{run} command. For example,
2073 starts your program, diverting its output to the file @file{outfile}.
2076 @cindex controlling terminal
2077 Another way to specify where your program should do input and output is
2078 with the @code{tty} command. This command accepts a file name as
2079 argument, and causes this file to be the default for future @code{run}
2080 commands. It also resets the controlling terminal for the child
2081 process, for future @code{run} commands. For example,
2088 directs that processes started with subsequent @code{run} commands
2089 default to do input and output on the terminal @file{/dev/ttyb} and have
2090 that as their controlling terminal.
2092 An explicit redirection in @code{run} overrides the @code{tty} command's
2093 effect on the input/output device, but not its effect on the controlling
2096 When you use the @code{tty} command or redirect input in the @code{run}
2097 command, only the input @emph{for your program} is affected. The input
2098 for @value{GDBN} still comes from your terminal.
2101 @section Debugging an already-running process
2106 @item attach @var{process-id}
2107 This command attaches to a running process---one that was started
2108 outside @value{GDBN}. (@code{info files} shows your active
2109 targets.) The command takes as argument a process ID. The usual way to
2110 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2111 or with the @samp{jobs -l} shell command.
2113 @code{attach} does not repeat if you press @key{RET} a second time after
2114 executing the command.
2117 To use @code{attach}, your program must be running in an environment
2118 which supports processes; for example, @code{attach} does not work for
2119 programs on bare-board targets that lack an operating system. You must
2120 also have permission to send the process a signal.
2122 When you use @code{attach}, the debugger finds the program running in
2123 the process first by looking in the current working directory, then (if
2124 the program is not found) by using the source file search path
2125 (@pxref{Source Path, ,Specifying source directories}). You can also use
2126 the @code{file} command to load the program. @xref{Files, ,Commands to
2129 The first thing @value{GDBN} does after arranging to debug the specified
2130 process is to stop it. You can examine and modify an attached process
2131 with all the @value{GDBN} commands that are ordinarily available when
2132 you start processes with @code{run}. You can insert breakpoints; you
2133 can step and continue; you can modify storage. If you would rather the
2134 process continue running, you may use the @code{continue} command after
2135 attaching @value{GDBN} to the process.
2140 When you have finished debugging the attached process, you can use the
2141 @code{detach} command to release it from @value{GDBN} control. Detaching
2142 the process continues its execution. After the @code{detach} command,
2143 that process and @value{GDBN} become completely independent once more, and you
2144 are ready to @code{attach} another process or start one with @code{run}.
2145 @code{detach} does not repeat if you press @key{RET} again after
2146 executing the command.
2149 If you exit @value{GDBN} or use the @code{run} command while you have an
2150 attached process, you kill that process. By default, @value{GDBN} asks
2151 for confirmation if you try to do either of these things; you can
2152 control whether or not you need to confirm by using the @code{set
2153 confirm} command (@pxref{Messages/Warnings, ,Optional warnings and
2157 @section Killing the child process
2162 Kill the child process in which your program is running under @value{GDBN}.
2165 This command is useful if you wish to debug a core dump instead of a
2166 running process. @value{GDBN} ignores any core dump file while your program
2169 On some operating systems, a program cannot be executed outside @value{GDBN}
2170 while you have breakpoints set on it inside @value{GDBN}. You can use the
2171 @code{kill} command in this situation to permit running your program
2172 outside the debugger.
2174 The @code{kill} command is also useful if you wish to recompile and
2175 relink your program, since on many systems it is impossible to modify an
2176 executable file while it is running in a process. In this case, when you
2177 next type @code{run}, @value{GDBN} notices that the file has changed, and
2178 reads the symbol table again (while trying to preserve your current
2179 breakpoint settings).
2182 @section Debugging programs with multiple threads
2184 @cindex threads of execution
2185 @cindex multiple threads
2186 @cindex switching threads
2187 In some operating systems, such as HP-UX and Solaris, a single program
2188 may have more than one @dfn{thread} of execution. The precise semantics
2189 of threads differ from one operating system to another, but in general
2190 the threads of a single program are akin to multiple processes---except
2191 that they share one address space (that is, they can all examine and
2192 modify the same variables). On the other hand, each thread has its own
2193 registers and execution stack, and perhaps private memory.
2195 @value{GDBN} provides these facilities for debugging multi-thread
2199 @item automatic notification of new threads
2200 @item @samp{thread @var{threadno}}, a command to switch among threads
2201 @item @samp{info threads}, a command to inquire about existing threads
2202 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2203 a command to apply a command to a list of threads
2204 @item thread-specific breakpoints
2208 @emph{Warning:} These facilities are not yet available on every
2209 @value{GDBN} configuration where the operating system supports threads.
2210 If your @value{GDBN} does not support threads, these commands have no
2211 effect. For example, a system without thread support shows no output
2212 from @samp{info threads}, and always rejects the @code{thread} command,
2216 (@value{GDBP}) info threads
2217 (@value{GDBP}) thread 1
2218 Thread ID 1 not known. Use the "info threads" command to
2219 see the IDs of currently known threads.
2221 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2222 @c doesn't support threads"?
2225 @cindex focus of debugging
2226 @cindex current thread
2227 The @value{GDBN} thread debugging facility allows you to observe all
2228 threads while your program runs---but whenever @value{GDBN} takes
2229 control, one thread in particular is always the focus of debugging.
2230 This thread is called the @dfn{current thread}. Debugging commands show
2231 program information from the perspective of the current thread.
2233 @cindex @code{New} @var{systag} message
2234 @cindex thread identifier (system)
2235 @c FIXME-implementors!! It would be more helpful if the [New...] message
2236 @c included GDB's numeric thread handle, so you could just go to that
2237 @c thread without first checking `info threads'.
2238 Whenever @value{GDBN} detects a new thread in your program, it displays
2239 the target system's identification for the thread with a message in the
2240 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2241 whose form varies depending on the particular system. For example, on
2242 LynxOS, you might see
2245 [New process 35 thread 27]
2249 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2250 the @var{systag} is simply something like @samp{process 368}, with no
2253 @c FIXME!! (1) Does the [New...] message appear even for the very first
2254 @c thread of a program, or does it only appear for the
2255 @c second---i.e.@: when it becomes obvious we have a multithread
2257 @c (2) *Is* there necessarily a first thread always? Or do some
2258 @c multithread systems permit starting a program with multiple
2259 @c threads ab initio?
2261 @cindex thread number
2262 @cindex thread identifier (GDB)
2263 For debugging purposes, @value{GDBN} associates its own thread
2264 number---always a single integer---with each thread in your program.
2267 @kindex info threads
2269 Display a summary of all threads currently in your
2270 program. @value{GDBN} displays for each thread (in this order):
2274 the thread number assigned by @value{GDBN}
2277 the target system's thread identifier (@var{systag})
2280 the current stack frame summary for that thread
2284 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2285 indicates the current thread.
2289 @c end table here to get a little more width for example
2292 (@value{GDBP}) info threads
2293 3 process 35 thread 27 0x34e5 in sigpause ()
2294 2 process 35 thread 23 0x34e5 in sigpause ()
2295 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2301 @cindex debugging multithreaded programs (on HP-UX)
2302 @cindex thread identifier (GDB), on HP-UX
2303 For debugging purposes, @value{GDBN} associates its own thread
2304 number---a small integer assigned in thread-creation order---with each
2305 thread in your program.
2307 @cindex @code{New} @var{systag} message, on HP-UX
2308 @cindex thread identifier (system), on HP-UX
2309 @c FIXME-implementors!! It would be more helpful if the [New...] message
2310 @c included GDB's numeric thread handle, so you could just go to that
2311 @c thread without first checking `info threads'.
2312 Whenever @value{GDBN} detects a new thread in your program, it displays
2313 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2314 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2315 whose form varies depending on the particular system. For example, on
2319 [New thread 2 (system thread 26594)]
2323 when @value{GDBN} notices a new thread.
2326 @kindex info threads (HP-UX)
2328 Display a summary of all threads currently in your
2329 program. @value{GDBN} displays for each thread (in this order):
2332 @item the thread number assigned by @value{GDBN}
2334 @item the target system's thread identifier (@var{systag})
2336 @item the current stack frame summary for that thread
2340 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2341 indicates the current thread.
2345 @c end table here to get a little more width for example
2348 (@value{GDBP}) info threads
2349 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2351 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2352 from /usr/lib/libc.2
2353 1 system thread 27905 0x7b003498 in _brk () \@*
2354 from /usr/lib/libc.2
2357 On Solaris, you can display more information about user threads with a
2358 Solaris-specific command:
2361 @item maint info sol-threads
2362 @kindex maint info sol-threads
2363 @cindex thread info (Solaris)
2364 Display info on Solaris user threads.
2368 @kindex thread @var{threadno}
2369 @item thread @var{threadno}
2370 Make thread number @var{threadno} the current thread. The command
2371 argument @var{threadno} is the internal @value{GDBN} thread number, as
2372 shown in the first field of the @samp{info threads} display.
2373 @value{GDBN} responds by displaying the system identifier of the thread
2374 you selected, and its current stack frame summary:
2377 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2378 (@value{GDBP}) thread 2
2379 [Switching to process 35 thread 23]
2380 0x34e5 in sigpause ()
2384 As with the @samp{[New @dots{}]} message, the form of the text after
2385 @samp{Switching to} depends on your system's conventions for identifying
2388 @kindex thread apply
2389 @item thread apply [@var{threadno}] [@var{all}] @var{args}
2390 The @code{thread apply} command allows you to apply a command to one or
2391 more threads. Specify the numbers of the threads that you want affected
2392 with the command argument @var{threadno}. @var{threadno} is the internal
2393 @value{GDBN} thread number, as shown in the first field of the @samp{info
2394 threads} display. To apply a command to all threads, use
2395 @code{thread apply all} @var{args}.
2398 @cindex automatic thread selection
2399 @cindex switching threads automatically
2400 @cindex threads, automatic switching
2401 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2402 signal, it automatically selects the thread where that breakpoint or
2403 signal happened. @value{GDBN} alerts you to the context switch with a
2404 message of the form @samp{[Switching to @var{systag}]} to identify the
2407 @xref{Thread Stops,,Stopping and starting multi-thread programs}, for
2408 more information about how @value{GDBN} behaves when you stop and start
2409 programs with multiple threads.
2411 @xref{Set Watchpoints,,Setting watchpoints}, for information about
2412 watchpoints in programs with multiple threads.
2415 @section Debugging programs with multiple processes
2417 @cindex fork, debugging programs which call
2418 @cindex multiple processes
2419 @cindex processes, multiple
2420 On most systems, @value{GDBN} has no special support for debugging
2421 programs which create additional processes using the @code{fork}
2422 function. When a program forks, @value{GDBN} will continue to debug the
2423 parent process and the child process will run unimpeded. If you have
2424 set a breakpoint in any code which the child then executes, the child
2425 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2426 will cause it to terminate.
2428 However, if you want to debug the child process there is a workaround
2429 which isn't too painful. Put a call to @code{sleep} in the code which
2430 the child process executes after the fork. It may be useful to sleep
2431 only if a certain environment variable is set, or a certain file exists,
2432 so that the delay need not occur when you don't want to run @value{GDBN}
2433 on the child. While the child is sleeping, use the @code{ps} program to
2434 get its process ID. Then tell @value{GDBN} (a new invocation of
2435 @value{GDBN} if you are also debugging the parent process) to attach to
2436 the child process (@pxref{Attach}). From that point on you can debug
2437 the child process just like any other process which you attached to.
2439 On some systems, @value{GDBN} provides support for debugging programs that
2440 create additional processes using the @code{fork} or @code{vfork} functions.
2441 Currently, the only platforms with this feature are HP-UX (11.x and later
2442 only?) and GNU/Linux (kernel version 2.5.60 and later).
2444 By default, when a program forks, @value{GDBN} will continue to debug
2445 the parent process and the child process will run unimpeded.
2447 If you want to follow the child process instead of the parent process,
2448 use the command @w{@code{set follow-fork-mode}}.
2451 @kindex set follow-fork-mode
2452 @item set follow-fork-mode @var{mode}
2453 Set the debugger response to a program call of @code{fork} or
2454 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2455 process. The @var{mode} argument can be:
2459 The original process is debugged after a fork. The child process runs
2460 unimpeded. This is the default.
2463 The new process is debugged after a fork. The parent process runs
2468 @kindex show follow-fork-mode
2469 @item show follow-fork-mode
2470 Display the current debugger response to a @code{fork} or @code{vfork} call.
2473 If you ask to debug a child process and a @code{vfork} is followed by an
2474 @code{exec}, @value{GDBN} executes the new target up to the first
2475 breakpoint in the new target. If you have a breakpoint set on
2476 @code{main} in your original program, the breakpoint will also be set on
2477 the child process's @code{main}.
2479 When a child process is spawned by @code{vfork}, you cannot debug the
2480 child or parent until an @code{exec} call completes.
2482 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2483 call executes, the new target restarts. To restart the parent process,
2484 use the @code{file} command with the parent executable name as its
2487 You can use the @code{catch} command to make @value{GDBN} stop whenever
2488 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2489 Catchpoints, ,Setting catchpoints}.
2492 @chapter Stopping and Continuing
2494 The principal purposes of using a debugger are so that you can stop your
2495 program before it terminates; or so that, if your program runs into
2496 trouble, you can investigate and find out why.
2498 Inside @value{GDBN}, your program may stop for any of several reasons,
2499 such as a signal, a breakpoint, or reaching a new line after a
2500 @value{GDBN} command such as @code{step}. You may then examine and
2501 change variables, set new breakpoints or remove old ones, and then
2502 continue execution. Usually, the messages shown by @value{GDBN} provide
2503 ample explanation of the status of your program---but you can also
2504 explicitly request this information at any time.
2507 @kindex info program
2509 Display information about the status of your program: whether it is
2510 running or not, what process it is, and why it stopped.
2514 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2515 * Continuing and Stepping:: Resuming execution
2517 * Thread Stops:: Stopping and starting multi-thread programs
2521 @section Breakpoints, watchpoints, and catchpoints
2524 A @dfn{breakpoint} makes your program stop whenever a certain point in
2525 the program is reached. For each breakpoint, you can add conditions to
2526 control in finer detail whether your program stops. You can set
2527 breakpoints with the @code{break} command and its variants (@pxref{Set
2528 Breaks, ,Setting breakpoints}), to specify the place where your program
2529 should stop by line number, function name or exact address in the
2532 On some systems, you can set breakpoints in shared libraries before
2533 the executable is run. There is a minor limitation on HP-UX systems:
2534 you must wait until the executable is run in order to set breakpoints
2535 in shared library routines that are not called directly by the program
2536 (for example, routines that are arguments in a @code{pthread_create}
2540 @cindex memory tracing
2541 @cindex breakpoint on memory address
2542 @cindex breakpoint on variable modification
2543 A @dfn{watchpoint} is a special breakpoint that stops your program
2544 when the value of an expression changes. You must use a different
2545 command to set watchpoints (@pxref{Set Watchpoints, ,Setting
2546 watchpoints}), but aside from that, you can manage a watchpoint like
2547 any other breakpoint: you enable, disable, and delete both breakpoints
2548 and watchpoints using the same commands.
2550 You can arrange to have values from your program displayed automatically
2551 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2555 @cindex breakpoint on events
2556 A @dfn{catchpoint} is another special breakpoint that stops your program
2557 when a certain kind of event occurs, such as the throwing of a C@t{++}
2558 exception or the loading of a library. As with watchpoints, you use a
2559 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2560 catchpoints}), but aside from that, you can manage a catchpoint like any
2561 other breakpoint. (To stop when your program receives a signal, use the
2562 @code{handle} command; see @ref{Signals, ,Signals}.)
2564 @cindex breakpoint numbers
2565 @cindex numbers for breakpoints
2566 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2567 catchpoint when you create it; these numbers are successive integers
2568 starting with one. In many of the commands for controlling various
2569 features of breakpoints you use the breakpoint number to say which
2570 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2571 @dfn{disabled}; if disabled, it has no effect on your program until you
2574 @cindex breakpoint ranges
2575 @cindex ranges of breakpoints
2576 Some @value{GDBN} commands accept a range of breakpoints on which to
2577 operate. A breakpoint range is either a single breakpoint number, like
2578 @samp{5}, or two such numbers, in increasing order, separated by a
2579 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2580 all breakpoint in that range are operated on.
2583 * Set Breaks:: Setting breakpoints
2584 * Set Watchpoints:: Setting watchpoints
2585 * Set Catchpoints:: Setting catchpoints
2586 * Delete Breaks:: Deleting breakpoints
2587 * Disabling:: Disabling breakpoints
2588 * Conditions:: Break conditions
2589 * Break Commands:: Breakpoint command lists
2590 * Breakpoint Menus:: Breakpoint menus
2591 * Error in Breakpoints:: ``Cannot insert breakpoints''
2592 * Breakpoint related warnings:: ``Breakpoint address adjusted...''
2596 @subsection Setting breakpoints
2598 @c FIXME LMB what does GDB do if no code on line of breakpt?
2599 @c consider in particular declaration with/without initialization.
2601 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2604 @kindex b @r{(@code{break})}
2605 @vindex $bpnum@r{, convenience variable}
2606 @cindex latest breakpoint
2607 Breakpoints are set with the @code{break} command (abbreviated
2608 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2609 number of the breakpoint you've set most recently; see @ref{Convenience
2610 Vars,, Convenience variables}, for a discussion of what you can do with
2611 convenience variables.
2613 You have several ways to say where the breakpoint should go.
2616 @item break @var{function}
2617 Set a breakpoint at entry to function @var{function}.
2618 When using source languages that permit overloading of symbols, such as
2619 C@t{++}, @var{function} may refer to more than one possible place to break.
2620 @xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation.
2622 @item break +@var{offset}
2623 @itemx break -@var{offset}
2624 Set a breakpoint some number of lines forward or back from the position
2625 at which execution stopped in the currently selected @dfn{stack frame}.
2626 (@xref{Frames, ,Frames}, for a description of stack frames.)
2628 @item break @var{linenum}
2629 Set a breakpoint at line @var{linenum} in the current source file.
2630 The current source file is the last file whose source text was printed.
2631 The breakpoint will stop your program just before it executes any of the
2634 @item break @var{filename}:@var{linenum}
2635 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2637 @item break @var{filename}:@var{function}
2638 Set a breakpoint at entry to function @var{function} found in file
2639 @var{filename}. Specifying a file name as well as a function name is
2640 superfluous except when multiple files contain similarly named
2643 @item break *@var{address}
2644 Set a breakpoint at address @var{address}. You can use this to set
2645 breakpoints in parts of your program which do not have debugging
2646 information or source files.
2649 When called without any arguments, @code{break} sets a breakpoint at
2650 the next instruction to be executed in the selected stack frame
2651 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2652 innermost, this makes your program stop as soon as control
2653 returns to that frame. This is similar to the effect of a
2654 @code{finish} command in the frame inside the selected frame---except
2655 that @code{finish} does not leave an active breakpoint. If you use
2656 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2657 the next time it reaches the current location; this may be useful
2660 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2661 least one instruction has been executed. If it did not do this, you
2662 would be unable to proceed past a breakpoint without first disabling the
2663 breakpoint. This rule applies whether or not the breakpoint already
2664 existed when your program stopped.
2666 @item break @dots{} if @var{cond}
2667 Set a breakpoint with condition @var{cond}; evaluate the expression
2668 @var{cond} each time the breakpoint is reached, and stop only if the
2669 value is nonzero---that is, if @var{cond} evaluates as true.
2670 @samp{@dots{}} stands for one of the possible arguments described
2671 above (or no argument) specifying where to break. @xref{Conditions,
2672 ,Break conditions}, for more information on breakpoint conditions.
2675 @item tbreak @var{args}
2676 Set a breakpoint enabled only for one stop. @var{args} are the
2677 same as for the @code{break} command, and the breakpoint is set in the same
2678 way, but the breakpoint is automatically deleted after the first time your
2679 program stops there. @xref{Disabling, ,Disabling breakpoints}.
2682 @cindex hardware breakpoints
2683 @item hbreak @var{args}
2684 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2685 @code{break} command and the breakpoint is set in the same way, but the
2686 breakpoint requires hardware support and some target hardware may not
2687 have this support. The main purpose of this is EPROM/ROM code
2688 debugging, so you can set a breakpoint at an instruction without
2689 changing the instruction. This can be used with the new trap-generation
2690 provided by SPARClite DSU and most x86-based targets. These targets
2691 will generate traps when a program accesses some data or instruction
2692 address that is assigned to the debug registers. However the hardware
2693 breakpoint registers can take a limited number of breakpoints. For
2694 example, on the DSU, only two data breakpoints can be set at a time, and
2695 @value{GDBN} will reject this command if more than two are used. Delete
2696 or disable unused hardware breakpoints before setting new ones
2697 (@pxref{Disabling, ,Disabling}). @xref{Conditions, ,Break conditions}.
2698 For remote targets, you can restrict the number of hardware
2699 breakpoints @value{GDBN} will use, see @ref{set remote
2700 hardware-breakpoint-limit}.
2704 @item thbreak @var{args}
2705 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2706 are the same as for the @code{hbreak} command and the breakpoint is set in
2707 the same way. However, like the @code{tbreak} command,
2708 the breakpoint is automatically deleted after the
2709 first time your program stops there. Also, like the @code{hbreak}
2710 command, the breakpoint requires hardware support and some target hardware
2711 may not have this support. @xref{Disabling, ,Disabling breakpoints}.
2712 See also @ref{Conditions, ,Break conditions}.
2715 @cindex regular expression
2716 @cindex breakpoints in functions matching a regexp
2717 @cindex set breakpoints in many functions
2718 @item rbreak @var{regex}
2719 Set breakpoints on all functions matching the regular expression
2720 @var{regex}. This command sets an unconditional breakpoint on all
2721 matches, printing a list of all breakpoints it set. Once these
2722 breakpoints are set, they are treated just like the breakpoints set with
2723 the @code{break} command. You can delete them, disable them, or make
2724 them conditional the same way as any other breakpoint.
2726 The syntax of the regular expression is the standard one used with tools
2727 like @file{grep}. Note that this is different from the syntax used by
2728 shells, so for instance @code{foo*} matches all functions that include
2729 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2730 @code{.*} leading and trailing the regular expression you supply, so to
2731 match only functions that begin with @code{foo}, use @code{^foo}.
2733 @cindex non-member C@t{++} functions, set breakpoint in
2734 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2735 breakpoints on overloaded functions that are not members of any special
2738 @cindex set breakpoints on all functions
2739 The @code{rbreak} command can be used to set breakpoints in
2740 @strong{all} the functions in a program, like this:
2743 (@value{GDBP}) rbreak .
2746 @kindex info breakpoints
2747 @cindex @code{$_} and @code{info breakpoints}
2748 @item info breakpoints @r{[}@var{n}@r{]}
2749 @itemx info break @r{[}@var{n}@r{]}
2750 @itemx info watchpoints @r{[}@var{n}@r{]}
2751 Print a table of all breakpoints, watchpoints, and catchpoints set and
2752 not deleted, with the following columns for each breakpoint:
2755 @item Breakpoint Numbers
2757 Breakpoint, watchpoint, or catchpoint.
2759 Whether the breakpoint is marked to be disabled or deleted when hit.
2760 @item Enabled or Disabled
2761 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2762 that are not enabled.
2764 Where the breakpoint is in your program, as a memory address. If the
2765 breakpoint is pending (see below for details) on a future load of a shared library, the address
2766 will be listed as @samp{<PENDING>}.
2768 Where the breakpoint is in the source for your program, as a file and
2769 line number. For a pending breakpoint, the original string passed to
2770 the breakpoint command will be listed as it cannot be resolved until
2771 the appropriate shared library is loaded in the future.
2775 If a breakpoint is conditional, @code{info break} shows the condition on
2776 the line following the affected breakpoint; breakpoint commands, if any,
2777 are listed after that. A pending breakpoint is allowed to have a condition
2778 specified for it. The condition is not parsed for validity until a shared
2779 library is loaded that allows the pending breakpoint to resolve to a
2783 @code{info break} with a breakpoint
2784 number @var{n} as argument lists only that breakpoint. The
2785 convenience variable @code{$_} and the default examining-address for
2786 the @code{x} command are set to the address of the last breakpoint
2787 listed (@pxref{Memory, ,Examining memory}).
2790 @code{info break} displays a count of the number of times the breakpoint
2791 has been hit. This is especially useful in conjunction with the
2792 @code{ignore} command. You can ignore a large number of breakpoint
2793 hits, look at the breakpoint info to see how many times the breakpoint
2794 was hit, and then run again, ignoring one less than that number. This
2795 will get you quickly to the last hit of that breakpoint.
2798 @value{GDBN} allows you to set any number of breakpoints at the same place in
2799 your program. There is nothing silly or meaningless about this. When
2800 the breakpoints are conditional, this is even useful
2801 (@pxref{Conditions, ,Break conditions}).
2803 @cindex pending breakpoints
2804 If a specified breakpoint location cannot be found, it may be due to the fact
2805 that the location is in a shared library that is yet to be loaded. In such
2806 a case, you may want @value{GDBN} to create a special breakpoint (known as
2807 a @dfn{pending breakpoint}) that
2808 attempts to resolve itself in the future when an appropriate shared library
2811 Pending breakpoints are useful to set at the start of your
2812 @value{GDBN} session for locations that you know will be dynamically loaded
2813 later by the program being debugged. When shared libraries are loaded,
2814 a check is made to see if the load resolves any pending breakpoint locations.
2815 If a pending breakpoint location gets resolved,
2816 a regular breakpoint is created and the original pending breakpoint is removed.
2818 @value{GDBN} provides some additional commands for controlling pending
2821 @kindex set breakpoint pending
2822 @kindex show breakpoint pending
2824 @item set breakpoint pending auto
2825 This is the default behavior. When @value{GDBN} cannot find the breakpoint
2826 location, it queries you whether a pending breakpoint should be created.
2828 @item set breakpoint pending on
2829 This indicates that an unrecognized breakpoint location should automatically
2830 result in a pending breakpoint being created.
2832 @item set breakpoint pending off
2833 This indicates that pending breakpoints are not to be created. Any
2834 unrecognized breakpoint location results in an error. This setting does
2835 not affect any pending breakpoints previously created.
2837 @item show breakpoint pending
2838 Show the current behavior setting for creating pending breakpoints.
2841 @cindex operations allowed on pending breakpoints
2842 Normal breakpoint operations apply to pending breakpoints as well. You may
2843 specify a condition for a pending breakpoint and/or commands to run when the
2844 breakpoint is reached. You can also enable or disable
2845 the pending breakpoint. When you specify a condition for a pending breakpoint,
2846 the parsing of the condition will be deferred until the point where the
2847 pending breakpoint location is resolved. Disabling a pending breakpoint
2848 tells @value{GDBN} to not attempt to resolve the breakpoint on any subsequent
2849 shared library load. When a pending breakpoint is re-enabled,
2850 @value{GDBN} checks to see if the location is already resolved.
2851 This is done because any number of shared library loads could have
2852 occurred since the time the breakpoint was disabled and one or more
2853 of these loads could resolve the location.
2855 @cindex negative breakpoint numbers
2856 @cindex internal @value{GDBN} breakpoints
2857 @value{GDBN} itself sometimes sets breakpoints in your program for
2858 special purposes, such as proper handling of @code{longjmp} (in C
2859 programs). These internal breakpoints are assigned negative numbers,
2860 starting with @code{-1}; @samp{info breakpoints} does not display them.
2861 You can see these breakpoints with the @value{GDBN} maintenance command
2862 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
2865 @node Set Watchpoints
2866 @subsection Setting watchpoints
2868 @cindex setting watchpoints
2869 You can use a watchpoint to stop execution whenever the value of an
2870 expression changes, without having to predict a particular place where
2873 @cindex software watchpoints
2874 @cindex hardware watchpoints
2875 Depending on your system, watchpoints may be implemented in software or
2876 hardware. @value{GDBN} does software watchpointing by single-stepping your
2877 program and testing the variable's value each time, which is hundreds of
2878 times slower than normal execution. (But this may still be worth it, to
2879 catch errors where you have no clue what part of your program is the
2882 On some systems, such as HP-UX, @sc{gnu}/Linux and most other
2883 x86-based targets, @value{GDBN} includes support for hardware
2884 watchpoints, which do not slow down the running of your program.
2888 @item watch @var{expr}
2889 Set a watchpoint for an expression. @value{GDBN} will break when @var{expr}
2890 is written into by the program and its value changes.
2893 @item rwatch @var{expr}
2894 Set a watchpoint that will break when the value of @var{expr} is read
2898 @item awatch @var{expr}
2899 Set a watchpoint that will break when @var{expr} is either read from
2900 or written into by the program.
2902 @kindex info watchpoints
2903 @item info watchpoints
2904 This command prints a list of watchpoints, breakpoints, and catchpoints;
2905 it is the same as @code{info break} (@pxref{Set Breaks}).
2908 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
2909 watchpoints execute very quickly, and the debugger reports a change in
2910 value at the exact instruction where the change occurs. If @value{GDBN}
2911 cannot set a hardware watchpoint, it sets a software watchpoint, which
2912 executes more slowly and reports the change in value at the next
2913 @emph{statement}, not the instruction, after the change occurs.
2915 @cindex use only software watchpoints
2916 You can force @value{GDBN} to use only software watchpoints with the
2917 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
2918 zero, @value{GDBN} will never try to use hardware watchpoints, even if
2919 the underlying system supports them. (Note that hardware-assisted
2920 watchpoints that were set @emph{before} setting
2921 @code{can-use-hw-watchpoints} to zero will still use the hardware
2922 mechanism of watching expressiion values.)
2925 @item set can-use-hw-watchpoints
2926 @kindex set can-use-hw-watchpoints
2927 Set whether or not to use hardware watchpoints.
2929 @item show can-use-hw-watchpoints
2930 @kindex show can-use-hw-watchpoints
2931 Show the current mode of using hardware watchpoints.
2934 For remote targets, you can restrict the number of hardware
2935 watchpoints @value{GDBN} will use, see @ref{set remote
2936 hardware-breakpoint-limit}.
2938 When you issue the @code{watch} command, @value{GDBN} reports
2941 Hardware watchpoint @var{num}: @var{expr}
2945 if it was able to set a hardware watchpoint.
2947 Currently, the @code{awatch} and @code{rwatch} commands can only set
2948 hardware watchpoints, because accesses to data that don't change the
2949 value of the watched expression cannot be detected without examining
2950 every instruction as it is being executed, and @value{GDBN} does not do
2951 that currently. If @value{GDBN} finds that it is unable to set a
2952 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
2953 will print a message like this:
2956 Expression cannot be implemented with read/access watchpoint.
2959 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
2960 data type of the watched expression is wider than what a hardware
2961 watchpoint on the target machine can handle. For example, some systems
2962 can only watch regions that are up to 4 bytes wide; on such systems you
2963 cannot set hardware watchpoints for an expression that yields a
2964 double-precision floating-point number (which is typically 8 bytes
2965 wide). As a work-around, it might be possible to break the large region
2966 into a series of smaller ones and watch them with separate watchpoints.
2968 If you set too many hardware watchpoints, @value{GDBN} might be unable
2969 to insert all of them when you resume the execution of your program.
2970 Since the precise number of active watchpoints is unknown until such
2971 time as the program is about to be resumed, @value{GDBN} might not be
2972 able to warn you about this when you set the watchpoints, and the
2973 warning will be printed only when the program is resumed:
2976 Hardware watchpoint @var{num}: Could not insert watchpoint
2980 If this happens, delete or disable some of the watchpoints.
2982 The SPARClite DSU will generate traps when a program accesses some data
2983 or instruction address that is assigned to the debug registers. For the
2984 data addresses, DSU facilitates the @code{watch} command. However the
2985 hardware breakpoint registers can only take two data watchpoints, and
2986 both watchpoints must be the same kind. For example, you can set two
2987 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
2988 @strong{or} two with @code{awatch} commands, but you cannot set one
2989 watchpoint with one command and the other with a different command.
2990 @value{GDBN} will reject the command if you try to mix watchpoints.
2991 Delete or disable unused watchpoint commands before setting new ones.
2993 If you call a function interactively using @code{print} or @code{call},
2994 any watchpoints you have set will be inactive until @value{GDBN} reaches another
2995 kind of breakpoint or the call completes.
2997 @value{GDBN} automatically deletes watchpoints that watch local
2998 (automatic) variables, or expressions that involve such variables, when
2999 they go out of scope, that is, when the execution leaves the block in
3000 which these variables were defined. In particular, when the program
3001 being debugged terminates, @emph{all} local variables go out of scope,
3002 and so only watchpoints that watch global variables remain set. If you
3003 rerun the program, you will need to set all such watchpoints again. One
3004 way of doing that would be to set a code breakpoint at the entry to the
3005 @code{main} function and when it breaks, set all the watchpoints.
3008 @cindex watchpoints and threads
3009 @cindex threads and watchpoints
3010 @emph{Warning:} In multi-thread programs, watchpoints have only limited
3011 usefulness. With the current watchpoint implementation, @value{GDBN}
3012 can only watch the value of an expression @emph{in a single thread}. If
3013 you are confident that the expression can only change due to the current
3014 thread's activity (and if you are also confident that no other thread
3015 can become current), then you can use watchpoints as usual. However,
3016 @value{GDBN} may not notice when a non-current thread's activity changes
3019 @c FIXME: this is almost identical to the previous paragraph.
3020 @emph{HP-UX Warning:} In multi-thread programs, software watchpoints
3021 have only limited usefulness. If @value{GDBN} creates a software
3022 watchpoint, it can only watch the value of an expression @emph{in a
3023 single thread}. If you are confident that the expression can only
3024 change due to the current thread's activity (and if you are also
3025 confident that no other thread can become current), then you can use
3026 software watchpoints as usual. However, @value{GDBN} may not notice
3027 when a non-current thread's activity changes the expression. (Hardware
3028 watchpoints, in contrast, watch an expression in all threads.)
3031 @xref{set remote hardware-watchpoint-limit}.
3033 @node Set Catchpoints
3034 @subsection Setting catchpoints
3035 @cindex catchpoints, setting
3036 @cindex exception handlers
3037 @cindex event handling
3039 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3040 kinds of program events, such as C@t{++} exceptions or the loading of a
3041 shared library. Use the @code{catch} command to set a catchpoint.
3045 @item catch @var{event}
3046 Stop when @var{event} occurs. @var{event} can be any of the following:
3049 @cindex stop on C@t{++} exceptions
3050 The throwing of a C@t{++} exception.
3053 The catching of a C@t{++} exception.
3056 @cindex break on fork/exec
3057 A call to @code{exec}. This is currently only available for HP-UX.
3060 A call to @code{fork}. This is currently only available for HP-UX.
3063 A call to @code{vfork}. This is currently only available for HP-UX.
3066 @itemx load @var{libname}
3067 @cindex break on load/unload of shared library
3068 The dynamic loading of any shared library, or the loading of the library
3069 @var{libname}. This is currently only available for HP-UX.
3072 @itemx unload @var{libname}
3073 The unloading of any dynamically loaded shared library, or the unloading
3074 of the library @var{libname}. This is currently only available for HP-UX.
3077 @item tcatch @var{event}
3078 Set a catchpoint that is enabled only for one stop. The catchpoint is
3079 automatically deleted after the first time the event is caught.
3083 Use the @code{info break} command to list the current catchpoints.
3085 There are currently some limitations to C@t{++} exception handling
3086 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3090 If you call a function interactively, @value{GDBN} normally returns
3091 control to you when the function has finished executing. If the call
3092 raises an exception, however, the call may bypass the mechanism that
3093 returns control to you and cause your program either to abort or to
3094 simply continue running until it hits a breakpoint, catches a signal
3095 that @value{GDBN} is listening for, or exits. This is the case even if
3096 you set a catchpoint for the exception; catchpoints on exceptions are
3097 disabled within interactive calls.
3100 You cannot raise an exception interactively.
3103 You cannot install an exception handler interactively.
3106 @cindex raise exceptions
3107 Sometimes @code{catch} is not the best way to debug exception handling:
3108 if you need to know exactly where an exception is raised, it is better to
3109 stop @emph{before} the exception handler is called, since that way you
3110 can see the stack before any unwinding takes place. If you set a
3111 breakpoint in an exception handler instead, it may not be easy to find
3112 out where the exception was raised.
3114 To stop just before an exception handler is called, you need some
3115 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3116 raised by calling a library function named @code{__raise_exception}
3117 which has the following ANSI C interface:
3120 /* @var{addr} is where the exception identifier is stored.
3121 @var{id} is the exception identifier. */
3122 void __raise_exception (void **addr, void *id);
3126 To make the debugger catch all exceptions before any stack
3127 unwinding takes place, set a breakpoint on @code{__raise_exception}
3128 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}).
3130 With a conditional breakpoint (@pxref{Conditions, ,Break conditions})
3131 that depends on the value of @var{id}, you can stop your program when
3132 a specific exception is raised. You can use multiple conditional
3133 breakpoints to stop your program when any of a number of exceptions are
3138 @subsection Deleting breakpoints
3140 @cindex clearing breakpoints, watchpoints, catchpoints
3141 @cindex deleting breakpoints, watchpoints, catchpoints
3142 It is often necessary to eliminate a breakpoint, watchpoint, or
3143 catchpoint once it has done its job and you no longer want your program
3144 to stop there. This is called @dfn{deleting} the breakpoint. A
3145 breakpoint that has been deleted no longer exists; it is forgotten.
3147 With the @code{clear} command you can delete breakpoints according to
3148 where they are in your program. With the @code{delete} command you can
3149 delete individual breakpoints, watchpoints, or catchpoints by specifying
3150 their breakpoint numbers.
3152 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3153 automatically ignores breakpoints on the first instruction to be executed
3154 when you continue execution without changing the execution address.
3159 Delete any breakpoints at the next instruction to be executed in the
3160 selected stack frame (@pxref{Selection, ,Selecting a frame}). When
3161 the innermost frame is selected, this is a good way to delete a
3162 breakpoint where your program just stopped.
3164 @item clear @var{function}
3165 @itemx clear @var{filename}:@var{function}
3166 Delete any breakpoints set at entry to the named @var{function}.
3168 @item clear @var{linenum}
3169 @itemx clear @var{filename}:@var{linenum}
3170 Delete any breakpoints set at or within the code of the specified
3171 @var{linenum} of the specified @var{filename}.
3173 @cindex delete breakpoints
3175 @kindex d @r{(@code{delete})}
3176 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3177 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3178 ranges specified as arguments. If no argument is specified, delete all
3179 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3180 confirm off}). You can abbreviate this command as @code{d}.
3184 @subsection Disabling breakpoints
3186 @cindex enable/disable a breakpoint
3187 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3188 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3189 it had been deleted, but remembers the information on the breakpoint so
3190 that you can @dfn{enable} it again later.
3192 You disable and enable breakpoints, watchpoints, and catchpoints with
3193 the @code{enable} and @code{disable} commands, optionally specifying one
3194 or more breakpoint numbers as arguments. Use @code{info break} or
3195 @code{info watch} to print a list of breakpoints, watchpoints, and
3196 catchpoints if you do not know which numbers to use.
3198 A breakpoint, watchpoint, or catchpoint can have any of four different
3199 states of enablement:
3203 Enabled. The breakpoint stops your program. A breakpoint set
3204 with the @code{break} command starts out in this state.
3206 Disabled. The breakpoint has no effect on your program.
3208 Enabled once. The breakpoint stops your program, but then becomes
3211 Enabled for deletion. The breakpoint stops your program, but
3212 immediately after it does so it is deleted permanently. A breakpoint
3213 set with the @code{tbreak} command starts out in this state.
3216 You can use the following commands to enable or disable breakpoints,
3217 watchpoints, and catchpoints:
3221 @kindex dis @r{(@code{disable})}
3222 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3223 Disable the specified breakpoints---or all breakpoints, if none are
3224 listed. A disabled breakpoint has no effect but is not forgotten. All
3225 options such as ignore-counts, conditions and commands are remembered in
3226 case the breakpoint is enabled again later. You may abbreviate
3227 @code{disable} as @code{dis}.
3230 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3231 Enable the specified breakpoints (or all defined breakpoints). They
3232 become effective once again in stopping your program.
3234 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3235 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3236 of these breakpoints immediately after stopping your program.
3238 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3239 Enable the specified breakpoints to work once, then die. @value{GDBN}
3240 deletes any of these breakpoints as soon as your program stops there.
3241 Breakpoints set by the @code{tbreak} command start out in this state.
3244 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3245 @c confusing: tbreak is also initially enabled.
3246 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3247 ,Setting breakpoints}), breakpoints that you set are initially enabled;
3248 subsequently, they become disabled or enabled only when you use one of
3249 the commands above. (The command @code{until} can set and delete a
3250 breakpoint of its own, but it does not change the state of your other
3251 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3255 @subsection Break conditions
3256 @cindex conditional breakpoints
3257 @cindex breakpoint conditions
3259 @c FIXME what is scope of break condition expr? Context where wanted?
3260 @c in particular for a watchpoint?
3261 The simplest sort of breakpoint breaks every time your program reaches a
3262 specified place. You can also specify a @dfn{condition} for a
3263 breakpoint. A condition is just a Boolean expression in your
3264 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3265 a condition evaluates the expression each time your program reaches it,
3266 and your program stops only if the condition is @emph{true}.
3268 This is the converse of using assertions for program validation; in that
3269 situation, you want to stop when the assertion is violated---that is,
3270 when the condition is false. In C, if you want to test an assertion expressed
3271 by the condition @var{assert}, you should set the condition
3272 @samp{! @var{assert}} on the appropriate breakpoint.
3274 Conditions are also accepted for watchpoints; you may not need them,
3275 since a watchpoint is inspecting the value of an expression anyhow---but
3276 it might be simpler, say, to just set a watchpoint on a variable name,
3277 and specify a condition that tests whether the new value is an interesting
3280 Break conditions can have side effects, and may even call functions in
3281 your program. This can be useful, for example, to activate functions
3282 that log program progress, or to use your own print functions to
3283 format special data structures. The effects are completely predictable
3284 unless there is another enabled breakpoint at the same address. (In
3285 that case, @value{GDBN} might see the other breakpoint first and stop your
3286 program without checking the condition of this one.) Note that
3287 breakpoint commands are usually more convenient and flexible than break
3289 purpose of performing side effects when a breakpoint is reached
3290 (@pxref{Break Commands, ,Breakpoint command lists}).
3292 Break conditions can be specified when a breakpoint is set, by using
3293 @samp{if} in the arguments to the @code{break} command. @xref{Set
3294 Breaks, ,Setting breakpoints}. They can also be changed at any time
3295 with the @code{condition} command.
3297 You can also use the @code{if} keyword with the @code{watch} command.
3298 The @code{catch} command does not recognize the @code{if} keyword;
3299 @code{condition} is the only way to impose a further condition on a
3304 @item condition @var{bnum} @var{expression}
3305 Specify @var{expression} as the break condition for breakpoint,
3306 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3307 breakpoint @var{bnum} stops your program only if the value of
3308 @var{expression} is true (nonzero, in C). When you use
3309 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3310 syntactic correctness, and to determine whether symbols in it have
3311 referents in the context of your breakpoint. If @var{expression} uses
3312 symbols not referenced in the context of the breakpoint, @value{GDBN}
3313 prints an error message:
3316 No symbol "foo" in current context.
3321 not actually evaluate @var{expression} at the time the @code{condition}
3322 command (or a command that sets a breakpoint with a condition, like
3323 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3325 @item condition @var{bnum}
3326 Remove the condition from breakpoint number @var{bnum}. It becomes
3327 an ordinary unconditional breakpoint.
3330 @cindex ignore count (of breakpoint)
3331 A special case of a breakpoint condition is to stop only when the
3332 breakpoint has been reached a certain number of times. This is so
3333 useful that there is a special way to do it, using the @dfn{ignore
3334 count} of the breakpoint. Every breakpoint has an ignore count, which
3335 is an integer. Most of the time, the ignore count is zero, and
3336 therefore has no effect. But if your program reaches a breakpoint whose
3337 ignore count is positive, then instead of stopping, it just decrements
3338 the ignore count by one and continues. As a result, if the ignore count
3339 value is @var{n}, the breakpoint does not stop the next @var{n} times
3340 your program reaches it.
3344 @item ignore @var{bnum} @var{count}
3345 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3346 The next @var{count} times the breakpoint is reached, your program's
3347 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3350 To make the breakpoint stop the next time it is reached, specify
3353 When you use @code{continue} to resume execution of your program from a
3354 breakpoint, you can specify an ignore count directly as an argument to
3355 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3356 Stepping,,Continuing and stepping}.
3358 If a breakpoint has a positive ignore count and a condition, the
3359 condition is not checked. Once the ignore count reaches zero,
3360 @value{GDBN} resumes checking the condition.
3362 You could achieve the effect of the ignore count with a condition such
3363 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3364 is decremented each time. @xref{Convenience Vars, ,Convenience
3368 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3371 @node Break Commands
3372 @subsection Breakpoint command lists
3374 @cindex breakpoint commands
3375 You can give any breakpoint (or watchpoint or catchpoint) a series of
3376 commands to execute when your program stops due to that breakpoint. For
3377 example, you might want to print the values of certain expressions, or
3378 enable other breakpoints.
3383 @item commands @r{[}@var{bnum}@r{]}
3384 @itemx @dots{} @var{command-list} @dots{}
3386 Specify a list of commands for breakpoint number @var{bnum}. The commands
3387 themselves appear on the following lines. Type a line containing just
3388 @code{end} to terminate the commands.
3390 To remove all commands from a breakpoint, type @code{commands} and
3391 follow it immediately with @code{end}; that is, give no commands.
3393 With no @var{bnum} argument, @code{commands} refers to the last
3394 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3395 recently encountered).
3398 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3399 disabled within a @var{command-list}.
3401 You can use breakpoint commands to start your program up again. Simply
3402 use the @code{continue} command, or @code{step}, or any other command
3403 that resumes execution.
3405 Any other commands in the command list, after a command that resumes
3406 execution, are ignored. This is because any time you resume execution
3407 (even with a simple @code{next} or @code{step}), you may encounter
3408 another breakpoint---which could have its own command list, leading to
3409 ambiguities about which list to execute.
3412 If the first command you specify in a command list is @code{silent}, the
3413 usual message about stopping at a breakpoint is not printed. This may
3414 be desirable for breakpoints that are to print a specific message and
3415 then continue. If none of the remaining commands print anything, you
3416 see no sign that the breakpoint was reached. @code{silent} is
3417 meaningful only at the beginning of a breakpoint command list.
3419 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3420 print precisely controlled output, and are often useful in silent
3421 breakpoints. @xref{Output, ,Commands for controlled output}.
3423 For example, here is how you could use breakpoint commands to print the
3424 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3430 printf "x is %d\n",x
3435 One application for breakpoint commands is to compensate for one bug so
3436 you can test for another. Put a breakpoint just after the erroneous line
3437 of code, give it a condition to detect the case in which something
3438 erroneous has been done, and give it commands to assign correct values
3439 to any variables that need them. End with the @code{continue} command
3440 so that your program does not stop, and start with the @code{silent}
3441 command so that no output is produced. Here is an example:
3452 @node Breakpoint Menus
3453 @subsection Breakpoint menus
3455 @cindex symbol overloading
3457 Some programming languages (notably C@t{++} and Objective-C) permit a
3458 single function name
3459 to be defined several times, for application in different contexts.
3460 This is called @dfn{overloading}. When a function name is overloaded,
3461 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3462 a breakpoint. If you realize this is a problem, you can use
3463 something like @samp{break @var{function}(@var{types})} to specify which
3464 particular version of the function you want. Otherwise, @value{GDBN} offers
3465 you a menu of numbered choices for different possible breakpoints, and
3466 waits for your selection with the prompt @samp{>}. The first two
3467 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3468 sets a breakpoint at each definition of @var{function}, and typing
3469 @kbd{0} aborts the @code{break} command without setting any new
3472 For example, the following session excerpt shows an attempt to set a
3473 breakpoint at the overloaded symbol @code{String::after}.
3474 We choose three particular definitions of that function name:
3476 @c FIXME! This is likely to change to show arg type lists, at least
3479 (@value{GDBP}) b String::after
3482 [2] file:String.cc; line number:867
3483 [3] file:String.cc; line number:860
3484 [4] file:String.cc; line number:875
3485 [5] file:String.cc; line number:853
3486 [6] file:String.cc; line number:846
3487 [7] file:String.cc; line number:735
3489 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3490 Breakpoint 2 at 0xb344: file String.cc, line 875.
3491 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3492 Multiple breakpoints were set.
3493 Use the "delete" command to delete unwanted
3499 @c @ifclear BARETARGET
3500 @node Error in Breakpoints
3501 @subsection ``Cannot insert breakpoints''
3503 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3505 Under some operating systems, breakpoints cannot be used in a program if
3506 any other process is running that program. In this situation,
3507 attempting to run or continue a program with a breakpoint causes
3508 @value{GDBN} to print an error message:
3511 Cannot insert breakpoints.
3512 The same program may be running in another process.
3515 When this happens, you have three ways to proceed:
3519 Remove or disable the breakpoints, then continue.
3522 Suspend @value{GDBN}, and copy the file containing your program to a new
3523 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3524 that @value{GDBN} should run your program under that name.
3525 Then start your program again.
3528 Relink your program so that the text segment is nonsharable, using the
3529 linker option @samp{-N}. The operating system limitation may not apply
3530 to nonsharable executables.
3534 A similar message can be printed if you request too many active
3535 hardware-assisted breakpoints and watchpoints:
3537 @c FIXME: the precise wording of this message may change; the relevant
3538 @c source change is not committed yet (Sep 3, 1999).
3540 Stopped; cannot insert breakpoints.
3541 You may have requested too many hardware breakpoints and watchpoints.
3545 This message is printed when you attempt to resume the program, since
3546 only then @value{GDBN} knows exactly how many hardware breakpoints and
3547 watchpoints it needs to insert.
3549 When this message is printed, you need to disable or remove some of the
3550 hardware-assisted breakpoints and watchpoints, and then continue.
3552 @node Breakpoint related warnings
3553 @subsection ``Breakpoint address adjusted...''
3554 @cindex breakpoint address adjusted
3556 Some processor architectures place constraints on the addresses at
3557 which breakpoints may be placed. For architectures thus constrained,
3558 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3559 with the constraints dictated by the architecture.
3561 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3562 a VLIW architecture in which a number of RISC-like instructions may be
3563 bundled together for parallel execution. The FR-V architecture
3564 constrains the location of a breakpoint instruction within such a
3565 bundle to the instruction with the lowest address. @value{GDBN}
3566 honors this constraint by adjusting a breakpoint's address to the
3567 first in the bundle.
3569 It is not uncommon for optimized code to have bundles which contain
3570 instructions from different source statements, thus it may happen that
3571 a breakpoint's address will be adjusted from one source statement to
3572 another. Since this adjustment may significantly alter @value{GDBN}'s
3573 breakpoint related behavior from what the user expects, a warning is
3574 printed when the breakpoint is first set and also when the breakpoint
3577 A warning like the one below is printed when setting a breakpoint
3578 that's been subject to address adjustment:
3581 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3584 Such warnings are printed both for user settable and @value{GDBN}'s
3585 internal breakpoints. If you see one of these warnings, you should
3586 verify that a breakpoint set at the adjusted address will have the
3587 desired affect. If not, the breakpoint in question may be removed and
3588 other breakpoints may be set which will have the desired behavior.
3589 E.g., it may be sufficient to place the breakpoint at a later
3590 instruction. A conditional breakpoint may also be useful in some
3591 cases to prevent the breakpoint from triggering too often.
3593 @value{GDBN} will also issue a warning when stopping at one of these
3594 adjusted breakpoints:
3597 warning: Breakpoint 1 address previously adjusted from 0x00010414
3601 When this warning is encountered, it may be too late to take remedial
3602 action except in cases where the breakpoint is hit earlier or more
3603 frequently than expected.
3605 @node Continuing and Stepping
3606 @section Continuing and stepping
3610 @cindex resuming execution
3611 @dfn{Continuing} means resuming program execution until your program
3612 completes normally. In contrast, @dfn{stepping} means executing just
3613 one more ``step'' of your program, where ``step'' may mean either one
3614 line of source code, or one machine instruction (depending on what
3615 particular command you use). Either when continuing or when stepping,
3616 your program may stop even sooner, due to a breakpoint or a signal. (If
3617 it stops due to a signal, you may want to use @code{handle}, or use
3618 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3622 @kindex c @r{(@code{continue})}
3623 @kindex fg @r{(resume foreground execution)}
3624 @item continue @r{[}@var{ignore-count}@r{]}
3625 @itemx c @r{[}@var{ignore-count}@r{]}
3626 @itemx fg @r{[}@var{ignore-count}@r{]}
3627 Resume program execution, at the address where your program last stopped;
3628 any breakpoints set at that address are bypassed. The optional argument
3629 @var{ignore-count} allows you to specify a further number of times to
3630 ignore a breakpoint at this location; its effect is like that of
3631 @code{ignore} (@pxref{Conditions, ,Break conditions}).
3633 The argument @var{ignore-count} is meaningful only when your program
3634 stopped due to a breakpoint. At other times, the argument to
3635 @code{continue} is ignored.
3637 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3638 debugged program is deemed to be the foreground program) are provided
3639 purely for convenience, and have exactly the same behavior as
3643 To resume execution at a different place, you can use @code{return}
3644 (@pxref{Returning, ,Returning from a function}) to go back to the
3645 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3646 different address}) to go to an arbitrary location in your program.
3648 A typical technique for using stepping is to set a breakpoint
3649 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and catchpoints}) at the
3650 beginning of the function or the section of your program where a problem
3651 is believed to lie, run your program until it stops at that breakpoint,
3652 and then step through the suspect area, examining the variables that are
3653 interesting, until you see the problem happen.
3657 @kindex s @r{(@code{step})}
3659 Continue running your program until control reaches a different source
3660 line, then stop it and return control to @value{GDBN}. This command is
3661 abbreviated @code{s}.
3664 @c "without debugging information" is imprecise; actually "without line
3665 @c numbers in the debugging information". (gcc -g1 has debugging info but
3666 @c not line numbers). But it seems complex to try to make that
3667 @c distinction here.
3668 @emph{Warning:} If you use the @code{step} command while control is
3669 within a function that was compiled without debugging information,
3670 execution proceeds until control reaches a function that does have
3671 debugging information. Likewise, it will not step into a function which
3672 is compiled without debugging information. To step through functions
3673 without debugging information, use the @code{stepi} command, described
3677 The @code{step} command only stops at the first instruction of a source
3678 line. This prevents the multiple stops that could otherwise occur in
3679 @code{switch} statements, @code{for} loops, etc. @code{step} continues
3680 to stop if a function that has debugging information is called within
3681 the line. In other words, @code{step} @emph{steps inside} any functions
3682 called within the line.
3684 Also, the @code{step} command only enters a function if there is line
3685 number information for the function. Otherwise it acts like the
3686 @code{next} command. This avoids problems when using @code{cc -gl}
3687 on MIPS machines. Previously, @code{step} entered subroutines if there
3688 was any debugging information about the routine.
3690 @item step @var{count}
3691 Continue running as in @code{step}, but do so @var{count} times. If a
3692 breakpoint is reached, or a signal not related to stepping occurs before
3693 @var{count} steps, stepping stops right away.
3696 @kindex n @r{(@code{next})}
3697 @item next @r{[}@var{count}@r{]}
3698 Continue to the next source line in the current (innermost) stack frame.
3699 This is similar to @code{step}, but function calls that appear within
3700 the line of code are executed without stopping. Execution stops when
3701 control reaches a different line of code at the original stack level
3702 that was executing when you gave the @code{next} command. This command
3703 is abbreviated @code{n}.
3705 An argument @var{count} is a repeat count, as for @code{step}.
3708 @c FIX ME!! Do we delete this, or is there a way it fits in with
3709 @c the following paragraph? --- Vctoria
3711 @c @code{next} within a function that lacks debugging information acts like
3712 @c @code{step}, but any function calls appearing within the code of the
3713 @c function are executed without stopping.
3715 The @code{next} command only stops at the first instruction of a
3716 source line. This prevents multiple stops that could otherwise occur in
3717 @code{switch} statements, @code{for} loops, etc.
3719 @kindex set step-mode
3721 @cindex functions without line info, and stepping
3722 @cindex stepping into functions with no line info
3723 @itemx set step-mode on
3724 The @code{set step-mode on} command causes the @code{step} command to
3725 stop at the first instruction of a function which contains no debug line
3726 information rather than stepping over it.
3728 This is useful in cases where you may be interested in inspecting the
3729 machine instructions of a function which has no symbolic info and do not
3730 want @value{GDBN} to automatically skip over this function.
3732 @item set step-mode off
3733 Causes the @code{step} command to step over any functions which contains no
3734 debug information. This is the default.
3736 @item show step-mode
3737 Show whether @value{GDBN} will stop in or step over functions without
3738 source line debug information.
3742 Continue running until just after function in the selected stack frame
3743 returns. Print the returned value (if any).
3745 Contrast this with the @code{return} command (@pxref{Returning,
3746 ,Returning from a function}).
3749 @kindex u @r{(@code{until})}
3750 @cindex run until specified location
3753 Continue running until a source line past the current line, in the
3754 current stack frame, is reached. This command is used to avoid single
3755 stepping through a loop more than once. It is like the @code{next}
3756 command, except that when @code{until} encounters a jump, it
3757 automatically continues execution until the program counter is greater
3758 than the address of the jump.
3760 This means that when you reach the end of a loop after single stepping
3761 though it, @code{until} makes your program continue execution until it
3762 exits the loop. In contrast, a @code{next} command at the end of a loop
3763 simply steps back to the beginning of the loop, which forces you to step
3764 through the next iteration.
3766 @code{until} always stops your program if it attempts to exit the current
3769 @code{until} may produce somewhat counterintuitive results if the order
3770 of machine code does not match the order of the source lines. For
3771 example, in the following excerpt from a debugging session, the @code{f}
3772 (@code{frame}) command shows that execution is stopped at line
3773 @code{206}; yet when we use @code{until}, we get to line @code{195}:
3777 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
3779 (@value{GDBP}) until
3780 195 for ( ; argc > 0; NEXTARG) @{
3783 This happened because, for execution efficiency, the compiler had
3784 generated code for the loop closure test at the end, rather than the
3785 start, of the loop---even though the test in a C @code{for}-loop is
3786 written before the body of the loop. The @code{until} command appeared
3787 to step back to the beginning of the loop when it advanced to this
3788 expression; however, it has not really gone to an earlier
3789 statement---not in terms of the actual machine code.
3791 @code{until} with no argument works by means of single
3792 instruction stepping, and hence is slower than @code{until} with an
3795 @item until @var{location}
3796 @itemx u @var{location}
3797 Continue running your program until either the specified location is
3798 reached, or the current stack frame returns. @var{location} is any of
3799 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
3800 ,Setting breakpoints}). This form of the command uses breakpoints, and
3801 hence is quicker than @code{until} without an argument. The specified
3802 location is actually reached only if it is in the current frame. This
3803 implies that @code{until} can be used to skip over recursive function
3804 invocations. For instance in the code below, if the current location is
3805 line @code{96}, issuing @code{until 99} will execute the program up to
3806 line @code{99} in the same invocation of factorial, i.e. after the inner
3807 invocations have returned.
3810 94 int factorial (int value)
3812 96 if (value > 1) @{
3813 97 value *= factorial (value - 1);
3820 @kindex advance @var{location}
3821 @itemx advance @var{location}
3822 Continue running the program up to the given @var{location}. An argument is
3823 required, which should be of the same form as arguments for the @code{break}
3824 command. Execution will also stop upon exit from the current stack
3825 frame. This command is similar to @code{until}, but @code{advance} will
3826 not skip over recursive function calls, and the target location doesn't
3827 have to be in the same frame as the current one.
3831 @kindex si @r{(@code{stepi})}
3833 @itemx stepi @var{arg}
3835 Execute one machine instruction, then stop and return to the debugger.
3837 It is often useful to do @samp{display/i $pc} when stepping by machine
3838 instructions. This makes @value{GDBN} automatically display the next
3839 instruction to be executed, each time your program stops. @xref{Auto
3840 Display,, Automatic display}.
3842 An argument is a repeat count, as in @code{step}.
3846 @kindex ni @r{(@code{nexti})}
3848 @itemx nexti @var{arg}
3850 Execute one machine instruction, but if it is a function call,
3851 proceed until the function returns.
3853 An argument is a repeat count, as in @code{next}.
3860 A signal is an asynchronous event that can happen in a program. The
3861 operating system defines the possible kinds of signals, and gives each
3862 kind a name and a number. For example, in Unix @code{SIGINT} is the
3863 signal a program gets when you type an interrupt character (often @kbd{C-c});
3864 @code{SIGSEGV} is the signal a program gets from referencing a place in
3865 memory far away from all the areas in use; @code{SIGALRM} occurs when
3866 the alarm clock timer goes off (which happens only if your program has
3867 requested an alarm).
3869 @cindex fatal signals
3870 Some signals, including @code{SIGALRM}, are a normal part of the
3871 functioning of your program. Others, such as @code{SIGSEGV}, indicate
3872 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
3873 program has not specified in advance some other way to handle the signal.
3874 @code{SIGINT} does not indicate an error in your program, but it is normally
3875 fatal so it can carry out the purpose of the interrupt: to kill the program.
3877 @value{GDBN} has the ability to detect any occurrence of a signal in your
3878 program. You can tell @value{GDBN} in advance what to do for each kind of
3881 @cindex handling signals
3882 Normally, @value{GDBN} is set up to let the non-erroneous signals like
3883 @code{SIGALRM} be silently passed to your program
3884 (so as not to interfere with their role in the program's functioning)
3885 but to stop your program immediately whenever an error signal happens.
3886 You can change these settings with the @code{handle} command.
3889 @kindex info signals
3893 Print a table of all the kinds of signals and how @value{GDBN} has been told to
3894 handle each one. You can use this to see the signal numbers of all
3895 the defined types of signals.
3897 @code{info handle} is an alias for @code{info signals}.
3900 @item handle @var{signal} @var{keywords}@dots{}
3901 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
3902 can be the number of a signal or its name (with or without the
3903 @samp{SIG} at the beginning); a list of signal numbers of the form
3904 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
3905 known signals. The @var{keywords} say what change to make.
3909 The keywords allowed by the @code{handle} command can be abbreviated.
3910 Their full names are:
3914 @value{GDBN} should not stop your program when this signal happens. It may
3915 still print a message telling you that the signal has come in.
3918 @value{GDBN} should stop your program when this signal happens. This implies
3919 the @code{print} keyword as well.
3922 @value{GDBN} should print a message when this signal happens.
3925 @value{GDBN} should not mention the occurrence of the signal at all. This
3926 implies the @code{nostop} keyword as well.
3930 @value{GDBN} should allow your program to see this signal; your program
3931 can handle the signal, or else it may terminate if the signal is fatal
3932 and not handled. @code{pass} and @code{noignore} are synonyms.
3936 @value{GDBN} should not allow your program to see this signal.
3937 @code{nopass} and @code{ignore} are synonyms.
3941 When a signal stops your program, the signal is not visible to the
3943 continue. Your program sees the signal then, if @code{pass} is in
3944 effect for the signal in question @emph{at that time}. In other words,
3945 after @value{GDBN} reports a signal, you can use the @code{handle}
3946 command with @code{pass} or @code{nopass} to control whether your
3947 program sees that signal when you continue.
3949 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
3950 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
3951 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
3954 You can also use the @code{signal} command to prevent your program from
3955 seeing a signal, or cause it to see a signal it normally would not see,
3956 or to give it any signal at any time. For example, if your program stopped
3957 due to some sort of memory reference error, you might store correct
3958 values into the erroneous variables and continue, hoping to see more
3959 execution; but your program would probably terminate immediately as
3960 a result of the fatal signal once it saw the signal. To prevent this,
3961 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
3965 @section Stopping and starting multi-thread programs
3967 When your program has multiple threads (@pxref{Threads,, Debugging
3968 programs with multiple threads}), you can choose whether to set
3969 breakpoints on all threads, or on a particular thread.
3972 @cindex breakpoints and threads
3973 @cindex thread breakpoints
3974 @kindex break @dots{} thread @var{threadno}
3975 @item break @var{linespec} thread @var{threadno}
3976 @itemx break @var{linespec} thread @var{threadno} if @dots{}
3977 @var{linespec} specifies source lines; there are several ways of
3978 writing them, but the effect is always to specify some source line.
3980 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
3981 to specify that you only want @value{GDBN} to stop the program when a
3982 particular thread reaches this breakpoint. @var{threadno} is one of the
3983 numeric thread identifiers assigned by @value{GDBN}, shown in the first
3984 column of the @samp{info threads} display.
3986 If you do not specify @samp{thread @var{threadno}} when you set a
3987 breakpoint, the breakpoint applies to @emph{all} threads of your
3990 You can use the @code{thread} qualifier on conditional breakpoints as
3991 well; in this case, place @samp{thread @var{threadno}} before the
3992 breakpoint condition, like this:
3995 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
4000 @cindex stopped threads
4001 @cindex threads, stopped
4002 Whenever your program stops under @value{GDBN} for any reason,
4003 @emph{all} threads of execution stop, not just the current thread. This
4004 allows you to examine the overall state of the program, including
4005 switching between threads, without worrying that things may change
4008 @cindex thread breakpoints and system calls
4009 @cindex system calls and thread breakpoints
4010 @cindex premature return from system calls
4011 There is an unfortunate side effect. If one thread stops for a
4012 breakpoint, or for some other reason, and another thread is blocked in a
4013 system call, then the system call may return prematurely. This is a
4014 consequence of the interaction between multiple threads and the signals
4015 that @value{GDBN} uses to implement breakpoints and other events that
4018 To handle this problem, your program should check the return value of
4019 each system call and react appropriately. This is good programming
4022 For example, do not write code like this:
4028 The call to @code{sleep} will return early if a different thread stops
4029 at a breakpoint or for some other reason.
4031 Instead, write this:
4036 unslept = sleep (unslept);
4039 A system call is allowed to return early, so the system is still
4040 conforming to its specification. But @value{GDBN} does cause your
4041 multi-threaded program to behave differently than it would without
4044 Also, @value{GDBN} uses internal breakpoints in the thread library to
4045 monitor certain events such as thread creation and thread destruction.
4046 When such an event happens, a system call in another thread may return
4047 prematurely, even though your program does not appear to stop.
4049 @cindex continuing threads
4050 @cindex threads, continuing
4051 Conversely, whenever you restart the program, @emph{all} threads start
4052 executing. @emph{This is true even when single-stepping} with commands
4053 like @code{step} or @code{next}.
4055 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4056 Since thread scheduling is up to your debugging target's operating
4057 system (not controlled by @value{GDBN}), other threads may
4058 execute more than one statement while the current thread completes a
4059 single step. Moreover, in general other threads stop in the middle of a
4060 statement, rather than at a clean statement boundary, when the program
4063 You might even find your program stopped in another thread after
4064 continuing or even single-stepping. This happens whenever some other
4065 thread runs into a breakpoint, a signal, or an exception before the
4066 first thread completes whatever you requested.
4068 On some OSes, you can lock the OS scheduler and thus allow only a single
4072 @item set scheduler-locking @var{mode}
4073 @cindex scheduler locking mode
4074 @cindex lock scheduler
4075 Set the scheduler locking mode. If it is @code{off}, then there is no
4076 locking and any thread may run at any time. If @code{on}, then only the
4077 current thread may run when the inferior is resumed. The @code{step}
4078 mode optimizes for single-stepping. It stops other threads from
4079 ``seizing the prompt'' by preempting the current thread while you are
4080 stepping. Other threads will only rarely (or never) get a chance to run
4081 when you step. They are more likely to run when you @samp{next} over a
4082 function call, and they are completely free to run when you use commands
4083 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4084 thread hits a breakpoint during its timeslice, they will never steal the
4085 @value{GDBN} prompt away from the thread that you are debugging.
4087 @item show scheduler-locking
4088 Display the current scheduler locking mode.
4093 @chapter Examining the Stack
4095 When your program has stopped, the first thing you need to know is where it
4096 stopped and how it got there.
4099 Each time your program performs a function call, information about the call
4101 That information includes the location of the call in your program,
4102 the arguments of the call,
4103 and the local variables of the function being called.
4104 The information is saved in a block of data called a @dfn{stack frame}.
4105 The stack frames are allocated in a region of memory called the @dfn{call
4108 When your program stops, the @value{GDBN} commands for examining the
4109 stack allow you to see all of this information.
4111 @cindex selected frame
4112 One of the stack frames is @dfn{selected} by @value{GDBN} and many
4113 @value{GDBN} commands refer implicitly to the selected frame. In
4114 particular, whenever you ask @value{GDBN} for the value of a variable in
4115 your program, the value is found in the selected frame. There are
4116 special @value{GDBN} commands to select whichever frame you are
4117 interested in. @xref{Selection, ,Selecting a frame}.
4119 When your program stops, @value{GDBN} automatically selects the
4120 currently executing frame and describes it briefly, similar to the
4121 @code{frame} command (@pxref{Frame Info, ,Information about a frame}).
4124 * Frames:: Stack frames
4125 * Backtrace:: Backtraces
4126 * Selection:: Selecting a frame
4127 * Frame Info:: Information on a frame
4132 @section Stack frames
4134 @cindex frame, definition
4136 The call stack is divided up into contiguous pieces called @dfn{stack
4137 frames}, or @dfn{frames} for short; each frame is the data associated
4138 with one call to one function. The frame contains the arguments given
4139 to the function, the function's local variables, and the address at
4140 which the function is executing.
4142 @cindex initial frame
4143 @cindex outermost frame
4144 @cindex innermost frame
4145 When your program is started, the stack has only one frame, that of the
4146 function @code{main}. This is called the @dfn{initial} frame or the
4147 @dfn{outermost} frame. Each time a function is called, a new frame is
4148 made. Each time a function returns, the frame for that function invocation
4149 is eliminated. If a function is recursive, there can be many frames for
4150 the same function. The frame for the function in which execution is
4151 actually occurring is called the @dfn{innermost} frame. This is the most
4152 recently created of all the stack frames that still exist.
4154 @cindex frame pointer
4155 Inside your program, stack frames are identified by their addresses. A
4156 stack frame consists of many bytes, each of which has its own address; each
4157 kind of computer has a convention for choosing one byte whose
4158 address serves as the address of the frame. Usually this address is kept
4159 in a register called the @dfn{frame pointer register}
4160 (@pxref{Registers, $fp}) while execution is going on in that frame.
4162 @cindex frame number
4163 @value{GDBN} assigns numbers to all existing stack frames, starting with
4164 zero for the innermost frame, one for the frame that called it,
4165 and so on upward. These numbers do not really exist in your program;
4166 they are assigned by @value{GDBN} to give you a way of designating stack
4167 frames in @value{GDBN} commands.
4169 @c The -fomit-frame-pointer below perennially causes hbox overflow
4170 @c underflow problems.
4171 @cindex frameless execution
4172 Some compilers provide a way to compile functions so that they operate
4173 without stack frames. (For example, the @value{GCC} option
4175 @samp{-fomit-frame-pointer}
4177 generates functions without a frame.)
4178 This is occasionally done with heavily used library functions to save
4179 the frame setup time. @value{GDBN} has limited facilities for dealing
4180 with these function invocations. If the innermost function invocation
4181 has no stack frame, @value{GDBN} nevertheless regards it as though
4182 it had a separate frame, which is numbered zero as usual, allowing
4183 correct tracing of the function call chain. However, @value{GDBN} has
4184 no provision for frameless functions elsewhere in the stack.
4187 @kindex frame@r{, command}
4188 @cindex current stack frame
4189 @item frame @var{args}
4190 The @code{frame} command allows you to move from one stack frame to another,
4191 and to print the stack frame you select. @var{args} may be either the
4192 address of the frame or the stack frame number. Without an argument,
4193 @code{frame} prints the current stack frame.
4195 @kindex select-frame
4196 @cindex selecting frame silently
4198 The @code{select-frame} command allows you to move from one stack frame
4199 to another without printing the frame. This is the silent version of
4207 @cindex call stack traces
4208 A backtrace is a summary of how your program got where it is. It shows one
4209 line per frame, for many frames, starting with the currently executing
4210 frame (frame zero), followed by its caller (frame one), and on up the
4215 @kindex bt @r{(@code{backtrace})}
4218 Print a backtrace of the entire stack: one line per frame for all
4219 frames in the stack.
4221 You can stop the backtrace at any time by typing the system interrupt
4222 character, normally @kbd{C-c}.
4224 @item backtrace @var{n}
4226 Similar, but print only the innermost @var{n} frames.
4228 @item backtrace -@var{n}
4230 Similar, but print only the outermost @var{n} frames.
4232 @item backtrace full
4233 Print the values of the local variables also.
4239 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4240 are additional aliases for @code{backtrace}.
4242 Each line in the backtrace shows the frame number and the function name.
4243 The program counter value is also shown---unless you use @code{set
4244 print address off}. The backtrace also shows the source file name and
4245 line number, as well as the arguments to the function. The program
4246 counter value is omitted if it is at the beginning of the code for that
4249 Here is an example of a backtrace. It was made with the command
4250 @samp{bt 3}, so it shows the innermost three frames.
4254 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4256 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4257 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4259 (More stack frames follow...)
4264 The display for frame zero does not begin with a program counter
4265 value, indicating that your program has stopped at the beginning of the
4266 code for line @code{993} of @code{builtin.c}.
4268 @cindex value optimized out, in backtrace
4269 @cindex function call arguments, optimized out
4270 If your program was compiled with optimizations, some compilers will
4271 optimize away arguments passed to functions if those arguments are
4272 never used after the call. Such optimizations generate code that
4273 passes arguments through registers, but doesn't store those arguments
4274 in the stack frame. @value{GDBN} has no way of displaying such
4275 arguments in stack frames other than the innermost one. Here's what
4276 such a backtrace might look like:
4280 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4282 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
4283 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
4285 (More stack frames follow...)
4290 The values of arguments that were not saved in their stack frames are
4291 shown as @samp{<value optimized out>}.
4293 If you need to display the values of such optimized-out arguments,
4294 either deduce that from other variables whose values depend on the one
4295 you are interested in, or recompile without optimizations.
4297 @cindex backtrace beyond @code{main} function
4298 @cindex program entry point
4299 @cindex startup code, and backtrace
4300 Most programs have a standard user entry point---a place where system
4301 libraries and startup code transition into user code. For C this is
4302 @code{main}. When @value{GDBN} finds the entry function in a backtrace
4303 it will terminate the backtrace, to avoid tracing into highly
4304 system-specific (and generally uninteresting) code.
4306 If you need to examine the startup code, or limit the number of levels
4307 in a backtrace, you can change this behavior:
4310 @item set backtrace past-main
4311 @itemx set backtrace past-main on
4312 @kindex set backtrace
4313 Backtraces will continue past the user entry point.
4315 @item set backtrace past-main off
4316 Backtraces will stop when they encounter the user entry point. This is the
4319 @item show backtrace past-main
4320 @kindex show backtrace
4321 Display the current user entry point backtrace policy.
4323 @item set backtrace past-entry
4324 @itemx set backtrace past-entry on
4325 Backtraces will continue past the internal entry point of an application.
4326 This entry point is encoded by the linker when the application is built,
4327 and is likely before the user entry point @code{main} (or equivalent) is called.
4329 @item set backtrace past-entry off
4330 Backtraces will stop when they encouter the internal entry point of an
4331 application. This is the default.
4333 @item show backtrace past-entry
4334 Display the current internal entry point backtrace policy.
4336 @item set backtrace limit @var{n}
4337 @itemx set backtrace limit 0
4338 @cindex backtrace limit
4339 Limit the backtrace to @var{n} levels. A value of zero means
4342 @item show backtrace limit
4343 Display the current limit on backtrace levels.
4347 @section Selecting a frame
4349 Most commands for examining the stack and other data in your program work on
4350 whichever stack frame is selected at the moment. Here are the commands for
4351 selecting a stack frame; all of them finish by printing a brief description
4352 of the stack frame just selected.
4355 @kindex frame@r{, selecting}
4356 @kindex f @r{(@code{frame})}
4359 Select frame number @var{n}. Recall that frame zero is the innermost
4360 (currently executing) frame, frame one is the frame that called the
4361 innermost one, and so on. The highest-numbered frame is the one for
4364 @item frame @var{addr}
4366 Select the frame at address @var{addr}. This is useful mainly if the
4367 chaining of stack frames has been damaged by a bug, making it
4368 impossible for @value{GDBN} to assign numbers properly to all frames. In
4369 addition, this can be useful when your program has multiple stacks and
4370 switches between them.
4372 On the SPARC architecture, @code{frame} needs two addresses to
4373 select an arbitrary frame: a frame pointer and a stack pointer.
4375 On the MIPS and Alpha architecture, it needs two addresses: a stack
4376 pointer and a program counter.
4378 On the 29k architecture, it needs three addresses: a register stack
4379 pointer, a program counter, and a memory stack pointer.
4380 @c note to future updaters: this is conditioned on a flag
4381 @c SETUP_ARBITRARY_FRAME in the tm-*.h files. The above is up to date
4382 @c as of 27 Jan 1994.
4386 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4387 advances toward the outermost frame, to higher frame numbers, to frames
4388 that have existed longer. @var{n} defaults to one.
4391 @kindex do @r{(@code{down})}
4393 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4394 advances toward the innermost frame, to lower frame numbers, to frames
4395 that were created more recently. @var{n} defaults to one. You may
4396 abbreviate @code{down} as @code{do}.
4399 All of these commands end by printing two lines of output describing the
4400 frame. The first line shows the frame number, the function name, the
4401 arguments, and the source file and line number of execution in that
4402 frame. The second line shows the text of that source line.
4410 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4412 10 read_input_file (argv[i]);
4416 After such a printout, the @code{list} command with no arguments
4417 prints ten lines centered on the point of execution in the frame.
4418 You can also edit the program at the point of execution with your favorite
4419 editing program by typing @code{edit}.
4420 @xref{List, ,Printing source lines},
4424 @kindex down-silently
4426 @item up-silently @var{n}
4427 @itemx down-silently @var{n}
4428 These two commands are variants of @code{up} and @code{down},
4429 respectively; they differ in that they do their work silently, without
4430 causing display of the new frame. They are intended primarily for use
4431 in @value{GDBN} command scripts, where the output might be unnecessary and
4436 @section Information about a frame
4438 There are several other commands to print information about the selected
4444 When used without any argument, this command does not change which
4445 frame is selected, but prints a brief description of the currently
4446 selected stack frame. It can be abbreviated @code{f}. With an
4447 argument, this command is used to select a stack frame.
4448 @xref{Selection, ,Selecting a frame}.
4451 @kindex info f @r{(@code{info frame})}
4454 This command prints a verbose description of the selected stack frame,
4459 the address of the frame
4461 the address of the next frame down (called by this frame)
4463 the address of the next frame up (caller of this frame)
4465 the language in which the source code corresponding to this frame is written
4467 the address of the frame's arguments
4469 the address of the frame's local variables
4471 the program counter saved in it (the address of execution in the caller frame)
4473 which registers were saved in the frame
4476 @noindent The verbose description is useful when
4477 something has gone wrong that has made the stack format fail to fit
4478 the usual conventions.
4480 @item info frame @var{addr}
4481 @itemx info f @var{addr}
4482 Print a verbose description of the frame at address @var{addr}, without
4483 selecting that frame. The selected frame remains unchanged by this
4484 command. This requires the same kind of address (more than one for some
4485 architectures) that you specify in the @code{frame} command.
4486 @xref{Selection, ,Selecting a frame}.
4490 Print the arguments of the selected frame, each on a separate line.
4494 Print the local variables of the selected frame, each on a separate
4495 line. These are all variables (declared either static or automatic)
4496 accessible at the point of execution of the selected frame.
4499 @cindex catch exceptions, list active handlers
4500 @cindex exception handlers, how to list
4502 Print a list of all the exception handlers that are active in the
4503 current stack frame at the current point of execution. To see other
4504 exception handlers, visit the associated frame (using the @code{up},
4505 @code{down}, or @code{frame} commands); then type @code{info catch}.
4506 @xref{Set Catchpoints, , Setting catchpoints}.
4512 @chapter Examining Source Files
4514 @value{GDBN} can print parts of your program's source, since the debugging
4515 information recorded in the program tells @value{GDBN} what source files were
4516 used to build it. When your program stops, @value{GDBN} spontaneously prints
4517 the line where it stopped. Likewise, when you select a stack frame
4518 (@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where
4519 execution in that frame has stopped. You can print other portions of
4520 source files by explicit command.
4522 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4523 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4524 @value{GDBN} under @sc{gnu} Emacs}.
4527 * List:: Printing source lines
4528 * Edit:: Editing source files
4529 * Search:: Searching source files
4530 * Source Path:: Specifying source directories
4531 * Machine Code:: Source and machine code
4535 @section Printing source lines
4538 @kindex l @r{(@code{list})}
4539 To print lines from a source file, use the @code{list} command
4540 (abbreviated @code{l}). By default, ten lines are printed.
4541 There are several ways to specify what part of the file you want to print.
4543 Here are the forms of the @code{list} command most commonly used:
4546 @item list @var{linenum}
4547 Print lines centered around line number @var{linenum} in the
4548 current source file.
4550 @item list @var{function}
4551 Print lines centered around the beginning of function
4555 Print more lines. If the last lines printed were printed with a
4556 @code{list} command, this prints lines following the last lines
4557 printed; however, if the last line printed was a solitary line printed
4558 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4559 Stack}), this prints lines centered around that line.
4562 Print lines just before the lines last printed.
4565 @cindex @code{list}, how many lines to display
4566 By default, @value{GDBN} prints ten source lines with any of these forms of
4567 the @code{list} command. You can change this using @code{set listsize}:
4570 @kindex set listsize
4571 @item set listsize @var{count}
4572 Make the @code{list} command display @var{count} source lines (unless
4573 the @code{list} argument explicitly specifies some other number).
4575 @kindex show listsize
4577 Display the number of lines that @code{list} prints.
4580 Repeating a @code{list} command with @key{RET} discards the argument,
4581 so it is equivalent to typing just @code{list}. This is more useful
4582 than listing the same lines again. An exception is made for an
4583 argument of @samp{-}; that argument is preserved in repetition so that
4584 each repetition moves up in the source file.
4587 In general, the @code{list} command expects you to supply zero, one or two
4588 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4589 of writing them, but the effect is always to specify some source line.
4590 Here is a complete description of the possible arguments for @code{list}:
4593 @item list @var{linespec}
4594 Print lines centered around the line specified by @var{linespec}.
4596 @item list @var{first},@var{last}
4597 Print lines from @var{first} to @var{last}. Both arguments are
4600 @item list ,@var{last}
4601 Print lines ending with @var{last}.
4603 @item list @var{first},
4604 Print lines starting with @var{first}.
4607 Print lines just after the lines last printed.
4610 Print lines just before the lines last printed.
4613 As described in the preceding table.
4616 Here are the ways of specifying a single source line---all the
4621 Specifies line @var{number} of the current source file.
4622 When a @code{list} command has two linespecs, this refers to
4623 the same source file as the first linespec.
4626 Specifies the line @var{offset} lines after the last line printed.
4627 When used as the second linespec in a @code{list} command that has
4628 two, this specifies the line @var{offset} lines down from the
4632 Specifies the line @var{offset} lines before the last line printed.
4634 @item @var{filename}:@var{number}
4635 Specifies line @var{number} in the source file @var{filename}.
4637 @item @var{function}
4638 Specifies the line that begins the body of the function @var{function}.
4639 For example: in C, this is the line with the open brace.
4641 @item @var{filename}:@var{function}
4642 Specifies the line of the open-brace that begins the body of the
4643 function @var{function} in the file @var{filename}. You only need the
4644 file name with a function name to avoid ambiguity when there are
4645 identically named functions in different source files.
4647 @item *@var{address}
4648 Specifies the line containing the program address @var{address}.
4649 @var{address} may be any expression.
4653 @section Editing source files
4654 @cindex editing source files
4657 @kindex e @r{(@code{edit})}
4658 To edit the lines in a source file, use the @code{edit} command.
4659 The editing program of your choice
4660 is invoked with the current line set to
4661 the active line in the program.
4662 Alternatively, there are several ways to specify what part of the file you
4663 want to print if you want to see other parts of the program.
4665 Here are the forms of the @code{edit} command most commonly used:
4669 Edit the current source file at the active line number in the program.
4671 @item edit @var{number}
4672 Edit the current source file with @var{number} as the active line number.
4674 @item edit @var{function}
4675 Edit the file containing @var{function} at the beginning of its definition.
4677 @item edit @var{filename}:@var{number}
4678 Specifies line @var{number} in the source file @var{filename}.
4680 @item edit @var{filename}:@var{function}
4681 Specifies the line that begins the body of the
4682 function @var{function} in the file @var{filename}. You only need the
4683 file name with a function name to avoid ambiguity when there are
4684 identically named functions in different source files.
4686 @item edit *@var{address}
4687 Specifies the line containing the program address @var{address}.
4688 @var{address} may be any expression.
4691 @subsection Choosing your editor
4692 You can customize @value{GDBN} to use any editor you want
4694 The only restriction is that your editor (say @code{ex}), recognizes the
4695 following command-line syntax:
4697 ex +@var{number} file
4699 The optional numeric value +@var{number} specifies the number of the line in
4700 the file where to start editing.}.
4701 By default, it is @file{@value{EDITOR}}, but you can change this
4702 by setting the environment variable @code{EDITOR} before using
4703 @value{GDBN}. For example, to configure @value{GDBN} to use the
4704 @code{vi} editor, you could use these commands with the @code{sh} shell:
4710 or in the @code{csh} shell,
4712 setenv EDITOR /usr/bin/vi
4717 @section Searching source files
4718 @cindex searching source files
4720 There are two commands for searching through the current source file for a
4725 @kindex forward-search
4726 @item forward-search @var{regexp}
4727 @itemx search @var{regexp}
4728 The command @samp{forward-search @var{regexp}} checks each line,
4729 starting with the one following the last line listed, for a match for
4730 @var{regexp}. It lists the line that is found. You can use the
4731 synonym @samp{search @var{regexp}} or abbreviate the command name as
4734 @kindex reverse-search
4735 @item reverse-search @var{regexp}
4736 The command @samp{reverse-search @var{regexp}} checks each line, starting
4737 with the one before the last line listed and going backward, for a match
4738 for @var{regexp}. It lists the line that is found. You can abbreviate
4739 this command as @code{rev}.
4743 @section Specifying source directories
4746 @cindex directories for source files
4747 Executable programs sometimes do not record the directories of the source
4748 files from which they were compiled, just the names. Even when they do,
4749 the directories could be moved between the compilation and your debugging
4750 session. @value{GDBN} has a list of directories to search for source files;
4751 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
4752 it tries all the directories in the list, in the order they are present
4753 in the list, until it finds a file with the desired name.
4755 For example, suppose an executable references the file
4756 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
4757 @file{/mnt/cross}. The file is first looked up literally; if this
4758 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
4759 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
4760 message is printed. @value{GDBN} does not look up the parts of the
4761 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
4762 Likewise, the subdirectories of the source path are not searched: if
4763 the source path is @file{/mnt/cross}, and the binary refers to
4764 @file{foo.c}, @value{GDBN} would not find it under
4765 @file{/mnt/cross/usr/src/foo-1.0/lib}.
4767 Plain file names, relative file names with leading directories, file
4768 names containing dots, etc.@: are all treated as described above; for
4769 instance, if the source path is @file{/mnt/cross}, and the source file
4770 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
4771 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
4772 that---@file{/mnt/cross/foo.c}.
4774 Note that the executable search path is @emph{not} used to locate the
4775 source files. Neither is the current working directory, unless it
4776 happens to be in the source path.
4778 Whenever you reset or rearrange the source path, @value{GDBN} clears out
4779 any information it has cached about where source files are found and where
4780 each line is in the file.
4784 When you start @value{GDBN}, its source path includes only @samp{cdir}
4785 and @samp{cwd}, in that order.
4786 To add other directories, use the @code{directory} command.
4789 @item directory @var{dirname} @dots{}
4790 @item dir @var{dirname} @dots{}
4791 Add directory @var{dirname} to the front of the source path. Several
4792 directory names may be given to this command, separated by @samp{:}
4793 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
4794 part of absolute file names) or
4795 whitespace. You may specify a directory that is already in the source
4796 path; this moves it forward, so @value{GDBN} searches it sooner.
4800 @vindex $cdir@r{, convenience variable}
4801 @vindex $cwdr@r{, convenience variable}
4802 @cindex compilation directory
4803 @cindex current directory
4804 @cindex working directory
4805 @cindex directory, current
4806 @cindex directory, compilation
4807 You can use the string @samp{$cdir} to refer to the compilation
4808 directory (if one is recorded), and @samp{$cwd} to refer to the current
4809 working directory. @samp{$cwd} is not the same as @samp{.}---the former
4810 tracks the current working directory as it changes during your @value{GDBN}
4811 session, while the latter is immediately expanded to the current
4812 directory at the time you add an entry to the source path.
4815 Reset the source path to empty again. This requires confirmation.
4817 @c RET-repeat for @code{directory} is explicitly disabled, but since
4818 @c repeating it would be a no-op we do not say that. (thanks to RMS)
4820 @item show directories
4821 @kindex show directories
4822 Print the source path: show which directories it contains.
4825 If your source path is cluttered with directories that are no longer of
4826 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
4827 versions of source. You can correct the situation as follows:
4831 Use @code{directory} with no argument to reset the source path to empty.
4834 Use @code{directory} with suitable arguments to reinstall the
4835 directories you want in the source path. You can add all the
4836 directories in one command.
4840 @section Source and machine code
4841 @cindex source line and its code address
4843 You can use the command @code{info line} to map source lines to program
4844 addresses (and vice versa), and the command @code{disassemble} to display
4845 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
4846 mode, the @code{info line} command causes the arrow to point to the
4847 line specified. Also, @code{info line} prints addresses in symbolic form as
4852 @item info line @var{linespec}
4853 Print the starting and ending addresses of the compiled code for
4854 source line @var{linespec}. You can specify source lines in any of
4855 the ways understood by the @code{list} command (@pxref{List, ,Printing
4859 For example, we can use @code{info line} to discover the location of
4860 the object code for the first line of function
4861 @code{m4_changequote}:
4863 @c FIXME: I think this example should also show the addresses in
4864 @c symbolic form, as they usually would be displayed.
4866 (@value{GDBP}) info line m4_changequote
4867 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
4871 @cindex code address and its source line
4872 We can also inquire (using @code{*@var{addr}} as the form for
4873 @var{linespec}) what source line covers a particular address:
4875 (@value{GDBP}) info line *0x63ff
4876 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
4879 @cindex @code{$_} and @code{info line}
4880 @cindex @code{x} command, default address
4881 @kindex x@r{(examine), and} info line
4882 After @code{info line}, the default address for the @code{x} command
4883 is changed to the starting address of the line, so that @samp{x/i} is
4884 sufficient to begin examining the machine code (@pxref{Memory,
4885 ,Examining memory}). Also, this address is saved as the value of the
4886 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
4891 @cindex assembly instructions
4892 @cindex instructions, assembly
4893 @cindex machine instructions
4894 @cindex listing machine instructions
4896 This specialized command dumps a range of memory as machine
4897 instructions. The default memory range is the function surrounding the
4898 program counter of the selected frame. A single argument to this
4899 command is a program counter value; @value{GDBN} dumps the function
4900 surrounding this value. Two arguments specify a range of addresses
4901 (first inclusive, second exclusive) to dump.
4904 The following example shows the disassembly of a range of addresses of
4905 HP PA-RISC 2.0 code:
4908 (@value{GDBP}) disas 0x32c4 0x32e4
4909 Dump of assembler code from 0x32c4 to 0x32e4:
4910 0x32c4 <main+204>: addil 0,dp
4911 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
4912 0x32cc <main+212>: ldil 0x3000,r31
4913 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
4914 0x32d4 <main+220>: ldo 0(r31),rp
4915 0x32d8 <main+224>: addil -0x800,dp
4916 0x32dc <main+228>: ldo 0x588(r1),r26
4917 0x32e0 <main+232>: ldil 0x3000,r31
4918 End of assembler dump.
4921 Some architectures have more than one commonly-used set of instruction
4922 mnemonics or other syntax.
4925 @kindex set disassembly-flavor
4926 @cindex Intel disassembly flavor
4927 @cindex AT&T disassembly flavor
4928 @item set disassembly-flavor @var{instruction-set}
4929 Select the instruction set to use when disassembling the
4930 program via the @code{disassemble} or @code{x/i} commands.
4932 Currently this command is only defined for the Intel x86 family. You
4933 can set @var{instruction-set} to either @code{intel} or @code{att}.
4934 The default is @code{att}, the AT&T flavor used by default by Unix
4935 assemblers for x86-based targets.
4937 @kindex show disassembly-flavor
4938 @item show disassembly-flavor
4939 Show the current setting of the disassembly flavor.
4944 @chapter Examining Data
4946 @cindex printing data
4947 @cindex examining data
4950 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
4951 @c document because it is nonstandard... Under Epoch it displays in a
4952 @c different window or something like that.
4953 The usual way to examine data in your program is with the @code{print}
4954 command (abbreviated @code{p}), or its synonym @code{inspect}. It
4955 evaluates and prints the value of an expression of the language your
4956 program is written in (@pxref{Languages, ,Using @value{GDBN} with
4957 Different Languages}).
4960 @item print @var{expr}
4961 @itemx print /@var{f} @var{expr}
4962 @var{expr} is an expression (in the source language). By default the
4963 value of @var{expr} is printed in a format appropriate to its data type;
4964 you can choose a different format by specifying @samp{/@var{f}}, where
4965 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
4969 @itemx print /@var{f}
4970 @cindex reprint the last value
4971 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
4972 @dfn{value history}; @pxref{Value History, ,Value history}). This allows you to
4973 conveniently inspect the same value in an alternative format.
4976 A more low-level way of examining data is with the @code{x} command.
4977 It examines data in memory at a specified address and prints it in a
4978 specified format. @xref{Memory, ,Examining memory}.
4980 If you are interested in information about types, or about how the
4981 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
4982 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
4986 * Expressions:: Expressions
4987 * Variables:: Program variables
4988 * Arrays:: Artificial arrays
4989 * Output Formats:: Output formats
4990 * Memory:: Examining memory
4991 * Auto Display:: Automatic display
4992 * Print Settings:: Print settings
4993 * Value History:: Value history
4994 * Convenience Vars:: Convenience variables
4995 * Registers:: Registers
4996 * Floating Point Hardware:: Floating point hardware
4997 * Vector Unit:: Vector Unit
4998 * OS Information:: Auxiliary data provided by operating system
4999 * Memory Region Attributes:: Memory region attributes
5000 * Dump/Restore Files:: Copy between memory and a file
5001 * Core File Generation:: Cause a program dump its core
5002 * Character Sets:: Debugging programs that use a different
5003 character set than GDB does
5004 * Caching Remote Data:: Data caching for remote targets
5008 @section Expressions
5011 @code{print} and many other @value{GDBN} commands accept an expression and
5012 compute its value. Any kind of constant, variable or operator defined
5013 by the programming language you are using is valid in an expression in
5014 @value{GDBN}. This includes conditional expressions, function calls,
5015 casts, and string constants. It also includes preprocessor macros, if
5016 you compiled your program to include this information; see
5019 @cindex arrays in expressions
5020 @value{GDBN} supports array constants in expressions input by
5021 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
5022 you can use the command @code{print @{1, 2, 3@}} to build up an array in
5023 memory that is @code{malloc}ed in the target program.
5025 Because C is so widespread, most of the expressions shown in examples in
5026 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
5027 Languages}, for information on how to use expressions in other
5030 In this section, we discuss operators that you can use in @value{GDBN}
5031 expressions regardless of your programming language.
5033 @cindex casts, in expressions
5034 Casts are supported in all languages, not just in C, because it is so
5035 useful to cast a number into a pointer in order to examine a structure
5036 at that address in memory.
5037 @c FIXME: casts supported---Mod2 true?
5039 @value{GDBN} supports these operators, in addition to those common
5040 to programming languages:
5044 @samp{@@} is a binary operator for treating parts of memory as arrays.
5045 @xref{Arrays, ,Artificial arrays}, for more information.
5048 @samp{::} allows you to specify a variable in terms of the file or
5049 function where it is defined. @xref{Variables, ,Program variables}.
5051 @cindex @{@var{type}@}
5052 @cindex type casting memory
5053 @cindex memory, viewing as typed object
5054 @cindex casts, to view memory
5055 @item @{@var{type}@} @var{addr}
5056 Refers to an object of type @var{type} stored at address @var{addr} in
5057 memory. @var{addr} may be any expression whose value is an integer or
5058 pointer (but parentheses are required around binary operators, just as in
5059 a cast). This construct is allowed regardless of what kind of data is
5060 normally supposed to reside at @var{addr}.
5064 @section Program variables
5066 The most common kind of expression to use is the name of a variable
5069 Variables in expressions are understood in the selected stack frame
5070 (@pxref{Selection, ,Selecting a frame}); they must be either:
5074 global (or file-static)
5081 visible according to the scope rules of the
5082 programming language from the point of execution in that frame
5085 @noindent This means that in the function
5100 you can examine and use the variable @code{a} whenever your program is
5101 executing within the function @code{foo}, but you can only use or
5102 examine the variable @code{b} while your program is executing inside
5103 the block where @code{b} is declared.
5105 @cindex variable name conflict
5106 There is an exception: you can refer to a variable or function whose
5107 scope is a single source file even if the current execution point is not
5108 in this file. But it is possible to have more than one such variable or
5109 function with the same name (in different source files). If that
5110 happens, referring to that name has unpredictable effects. If you wish,
5111 you can specify a static variable in a particular function or file,
5112 using the colon-colon (@code{::}) notation:
5114 @cindex colon-colon, context for variables/functions
5116 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
5117 @cindex @code{::}, context for variables/functions
5120 @var{file}::@var{variable}
5121 @var{function}::@var{variable}
5125 Here @var{file} or @var{function} is the name of the context for the
5126 static @var{variable}. In the case of file names, you can use quotes to
5127 make sure @value{GDBN} parses the file name as a single word---for example,
5128 to print a global value of @code{x} defined in @file{f2.c}:
5131 (@value{GDBP}) p 'f2.c'::x
5134 @cindex C@t{++} scope resolution
5135 This use of @samp{::} is very rarely in conflict with the very similar
5136 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
5137 scope resolution operator in @value{GDBN} expressions.
5138 @c FIXME: Um, so what happens in one of those rare cases where it's in
5141 @cindex wrong values
5142 @cindex variable values, wrong
5143 @cindex function entry/exit, wrong values of variables
5144 @cindex optimized code, wrong values of variables
5146 @emph{Warning:} Occasionally, a local variable may appear to have the
5147 wrong value at certain points in a function---just after entry to a new
5148 scope, and just before exit.
5150 You may see this problem when you are stepping by machine instructions.
5151 This is because, on most machines, it takes more than one instruction to
5152 set up a stack frame (including local variable definitions); if you are
5153 stepping by machine instructions, variables may appear to have the wrong
5154 values until the stack frame is completely built. On exit, it usually
5155 also takes more than one machine instruction to destroy a stack frame;
5156 after you begin stepping through that group of instructions, local
5157 variable definitions may be gone.
5159 This may also happen when the compiler does significant optimizations.
5160 To be sure of always seeing accurate values, turn off all optimization
5163 @cindex ``No symbol "foo" in current context''
5164 Another possible effect of compiler optimizations is to optimize
5165 unused variables out of existence, or assign variables to registers (as
5166 opposed to memory addresses). Depending on the support for such cases
5167 offered by the debug info format used by the compiler, @value{GDBN}
5168 might not be able to display values for such local variables. If that
5169 happens, @value{GDBN} will print a message like this:
5172 No symbol "foo" in current context.
5175 To solve such problems, either recompile without optimizations, or use a
5176 different debug info format, if the compiler supports several such
5177 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
5178 usually supports the @option{-gstabs+} option. @option{-gstabs+}
5179 produces debug info in a format that is superior to formats such as
5180 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
5181 an effective form for debug info. @xref{Debugging Options,,Options
5182 for Debugging Your Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}.
5183 @xref{C, , Debugging C++}, for more info about debug info formats
5184 that are best suited to C@t{++} programs.
5187 @section Artificial arrays
5189 @cindex artificial array
5191 @kindex @@@r{, referencing memory as an array}
5192 It is often useful to print out several successive objects of the
5193 same type in memory; a section of an array, or an array of
5194 dynamically determined size for which only a pointer exists in the
5197 You can do this by referring to a contiguous span of memory as an
5198 @dfn{artificial array}, using the binary operator @samp{@@}. The left
5199 operand of @samp{@@} should be the first element of the desired array
5200 and be an individual object. The right operand should be the desired length
5201 of the array. The result is an array value whose elements are all of
5202 the type of the left argument. The first element is actually the left
5203 argument; the second element comes from bytes of memory immediately
5204 following those that hold the first element, and so on. Here is an
5205 example. If a program says
5208 int *array = (int *) malloc (len * sizeof (int));
5212 you can print the contents of @code{array} with
5218 The left operand of @samp{@@} must reside in memory. Array values made
5219 with @samp{@@} in this way behave just like other arrays in terms of
5220 subscripting, and are coerced to pointers when used in expressions.
5221 Artificial arrays most often appear in expressions via the value history
5222 (@pxref{Value History, ,Value history}), after printing one out.
5224 Another way to create an artificial array is to use a cast.
5225 This re-interprets a value as if it were an array.
5226 The value need not be in memory:
5228 (@value{GDBP}) p/x (short[2])0x12345678
5229 $1 = @{0x1234, 0x5678@}
5232 As a convenience, if you leave the array length out (as in
5233 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
5234 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
5236 (@value{GDBP}) p/x (short[])0x12345678
5237 $2 = @{0x1234, 0x5678@}
5240 Sometimes the artificial array mechanism is not quite enough; in
5241 moderately complex data structures, the elements of interest may not
5242 actually be adjacent---for example, if you are interested in the values
5243 of pointers in an array. One useful work-around in this situation is
5244 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
5245 variables}) as a counter in an expression that prints the first
5246 interesting value, and then repeat that expression via @key{RET}. For
5247 instance, suppose you have an array @code{dtab} of pointers to
5248 structures, and you are interested in the values of a field @code{fv}
5249 in each structure. Here is an example of what you might type:
5259 @node Output Formats
5260 @section Output formats
5262 @cindex formatted output
5263 @cindex output formats
5264 By default, @value{GDBN} prints a value according to its data type. Sometimes
5265 this is not what you want. For example, you might want to print a number
5266 in hex, or a pointer in decimal. Or you might want to view data in memory
5267 at a certain address as a character string or as an instruction. To do
5268 these things, specify an @dfn{output format} when you print a value.
5270 The simplest use of output formats is to say how to print a value
5271 already computed. This is done by starting the arguments of the
5272 @code{print} command with a slash and a format letter. The format
5273 letters supported are:
5277 Regard the bits of the value as an integer, and print the integer in
5281 Print as integer in signed decimal.
5284 Print as integer in unsigned decimal.
5287 Print as integer in octal.
5290 Print as integer in binary. The letter @samp{t} stands for ``two''.
5291 @footnote{@samp{b} cannot be used because these format letters are also
5292 used with the @code{x} command, where @samp{b} stands for ``byte'';
5293 see @ref{Memory,,Examining memory}.}
5296 @cindex unknown address, locating
5297 @cindex locate address
5298 Print as an address, both absolute in hexadecimal and as an offset from
5299 the nearest preceding symbol. You can use this format used to discover
5300 where (in what function) an unknown address is located:
5303 (@value{GDBP}) p/a 0x54320
5304 $3 = 0x54320 <_initialize_vx+396>
5308 The command @code{info symbol 0x54320} yields similar results.
5309 @xref{Symbols, info symbol}.
5312 Regard as an integer and print it as a character constant. This
5313 prints both the numerical value and its character representation. The
5314 character representation is replaced with the octal escape @samp{\nnn}
5315 for characters outside the 7-bit @sc{ascii} range.
5318 Regard the bits of the value as a floating point number and print
5319 using typical floating point syntax.
5322 For example, to print the program counter in hex (@pxref{Registers}), type
5329 Note that no space is required before the slash; this is because command
5330 names in @value{GDBN} cannot contain a slash.
5332 To reprint the last value in the value history with a different format,
5333 you can use the @code{print} command with just a format and no
5334 expression. For example, @samp{p/x} reprints the last value in hex.
5337 @section Examining memory
5339 You can use the command @code{x} (for ``examine'') to examine memory in
5340 any of several formats, independently of your program's data types.
5342 @cindex examining memory
5344 @kindex x @r{(examine memory)}
5345 @item x/@var{nfu} @var{addr}
5348 Use the @code{x} command to examine memory.
5351 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
5352 much memory to display and how to format it; @var{addr} is an
5353 expression giving the address where you want to start displaying memory.
5354 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
5355 Several commands set convenient defaults for @var{addr}.
5358 @item @var{n}, the repeat count
5359 The repeat count is a decimal integer; the default is 1. It specifies
5360 how much memory (counting by units @var{u}) to display.
5361 @c This really is **decimal**; unaffected by 'set radix' as of GDB
5364 @item @var{f}, the display format
5365 The display format is one of the formats used by @code{print}
5366 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
5367 @samp{f}), and in addition @samp{s} (for null-terminated strings) and
5368 @samp{i} (for machine instructions). The default is @samp{x}
5369 (hexadecimal) initially. The default changes each time you use either
5370 @code{x} or @code{print}.
5372 @item @var{u}, the unit size
5373 The unit size is any of
5379 Halfwords (two bytes).
5381 Words (four bytes). This is the initial default.
5383 Giant words (eight bytes).
5386 Each time you specify a unit size with @code{x}, that size becomes the
5387 default unit the next time you use @code{x}. (For the @samp{s} and
5388 @samp{i} formats, the unit size is ignored and is normally not written.)
5390 @item @var{addr}, starting display address
5391 @var{addr} is the address where you want @value{GDBN} to begin displaying
5392 memory. The expression need not have a pointer value (though it may);
5393 it is always interpreted as an integer address of a byte of memory.
5394 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
5395 @var{addr} is usually just after the last address examined---but several
5396 other commands also set the default address: @code{info breakpoints} (to
5397 the address of the last breakpoint listed), @code{info line} (to the
5398 starting address of a line), and @code{print} (if you use it to display
5399 a value from memory).
5402 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
5403 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
5404 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
5405 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
5406 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
5408 Since the letters indicating unit sizes are all distinct from the
5409 letters specifying output formats, you do not have to remember whether
5410 unit size or format comes first; either order works. The output
5411 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
5412 (However, the count @var{n} must come first; @samp{wx4} does not work.)
5414 Even though the unit size @var{u} is ignored for the formats @samp{s}
5415 and @samp{i}, you might still want to use a count @var{n}; for example,
5416 @samp{3i} specifies that you want to see three machine instructions,
5417 including any operands. The command @code{disassemble} gives an
5418 alternative way of inspecting machine instructions; see @ref{Machine
5419 Code,,Source and machine code}.
5421 All the defaults for the arguments to @code{x} are designed to make it
5422 easy to continue scanning memory with minimal specifications each time
5423 you use @code{x}. For example, after you have inspected three machine
5424 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
5425 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
5426 the repeat count @var{n} is used again; the other arguments default as
5427 for successive uses of @code{x}.
5429 @cindex @code{$_}, @code{$__}, and value history
5430 The addresses and contents printed by the @code{x} command are not saved
5431 in the value history because there is often too much of them and they
5432 would get in the way. Instead, @value{GDBN} makes these values available for
5433 subsequent use in expressions as values of the convenience variables
5434 @code{$_} and @code{$__}. After an @code{x} command, the last address
5435 examined is available for use in expressions in the convenience variable
5436 @code{$_}. The contents of that address, as examined, are available in
5437 the convenience variable @code{$__}.
5439 If the @code{x} command has a repeat count, the address and contents saved
5440 are from the last memory unit printed; this is not the same as the last
5441 address printed if several units were printed on the last line of output.
5443 @cindex remote memory comparison
5444 @cindex verify remote memory image
5445 When you are debugging a program running on a remote target machine
5446 (@pxref{Remote}), you may wish to verify the program's image in the
5447 remote machine's memory against the executable file you downloaded to
5448 the target. The @code{compare-sections} command is provided for such
5452 @kindex compare-sections
5453 @item compare-sections @r{[}@var{section-name}@r{]}
5454 Compare the data of a loadable section @var{section-name} in the
5455 executable file of the program being debugged with the same section in
5456 the remote machine's memory, and report any mismatches. With no
5457 arguments, compares all loadable sections. This command's
5458 availability depends on the target's support for the @code{"qCRC"}
5463 @section Automatic display
5464 @cindex automatic display
5465 @cindex display of expressions
5467 If you find that you want to print the value of an expression frequently
5468 (to see how it changes), you might want to add it to the @dfn{automatic
5469 display list} so that @value{GDBN} prints its value each time your program stops.
5470 Each expression added to the list is given a number to identify it;
5471 to remove an expression from the list, you specify that number.
5472 The automatic display looks like this:
5476 3: bar[5] = (struct hack *) 0x3804
5480 This display shows item numbers, expressions and their current values. As with
5481 displays you request manually using @code{x} or @code{print}, you can
5482 specify the output format you prefer; in fact, @code{display} decides
5483 whether to use @code{print} or @code{x} depending on how elaborate your
5484 format specification is---it uses @code{x} if you specify a unit size,
5485 or one of the two formats (@samp{i} and @samp{s}) that are only
5486 supported by @code{x}; otherwise it uses @code{print}.
5490 @item display @var{expr}
5491 Add the expression @var{expr} to the list of expressions to display
5492 each time your program stops. @xref{Expressions, ,Expressions}.
5494 @code{display} does not repeat if you press @key{RET} again after using it.
5496 @item display/@var{fmt} @var{expr}
5497 For @var{fmt} specifying only a display format and not a size or
5498 count, add the expression @var{expr} to the auto-display list but
5499 arrange to display it each time in the specified format @var{fmt}.
5500 @xref{Output Formats,,Output formats}.
5502 @item display/@var{fmt} @var{addr}
5503 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
5504 number of units, add the expression @var{addr} as a memory address to
5505 be examined each time your program stops. Examining means in effect
5506 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}.
5509 For example, @samp{display/i $pc} can be helpful, to see the machine
5510 instruction about to be executed each time execution stops (@samp{$pc}
5511 is a common name for the program counter; @pxref{Registers, ,Registers}).
5514 @kindex delete display
5516 @item undisplay @var{dnums}@dots{}
5517 @itemx delete display @var{dnums}@dots{}
5518 Remove item numbers @var{dnums} from the list of expressions to display.
5520 @code{undisplay} does not repeat if you press @key{RET} after using it.
5521 (Otherwise you would just get the error @samp{No display number @dots{}}.)
5523 @kindex disable display
5524 @item disable display @var{dnums}@dots{}
5525 Disable the display of item numbers @var{dnums}. A disabled display
5526 item is not printed automatically, but is not forgotten. It may be
5527 enabled again later.
5529 @kindex enable display
5530 @item enable display @var{dnums}@dots{}
5531 Enable display of item numbers @var{dnums}. It becomes effective once
5532 again in auto display of its expression, until you specify otherwise.
5535 Display the current values of the expressions on the list, just as is
5536 done when your program stops.
5538 @kindex info display
5540 Print the list of expressions previously set up to display
5541 automatically, each one with its item number, but without showing the
5542 values. This includes disabled expressions, which are marked as such.
5543 It also includes expressions which would not be displayed right now
5544 because they refer to automatic variables not currently available.
5547 @cindex display disabled out of scope
5548 If a display expression refers to local variables, then it does not make
5549 sense outside the lexical context for which it was set up. Such an
5550 expression is disabled when execution enters a context where one of its
5551 variables is not defined. For example, if you give the command
5552 @code{display last_char} while inside a function with an argument
5553 @code{last_char}, @value{GDBN} displays this argument while your program
5554 continues to stop inside that function. When it stops elsewhere---where
5555 there is no variable @code{last_char}---the display is disabled
5556 automatically. The next time your program stops where @code{last_char}
5557 is meaningful, you can enable the display expression once again.
5559 @node Print Settings
5560 @section Print settings
5562 @cindex format options
5563 @cindex print settings
5564 @value{GDBN} provides the following ways to control how arrays, structures,
5565 and symbols are printed.
5568 These settings are useful for debugging programs in any language:
5572 @item set print address
5573 @itemx set print address on
5574 @cindex print/don't print memory addresses
5575 @value{GDBN} prints memory addresses showing the location of stack
5576 traces, structure values, pointer values, breakpoints, and so forth,
5577 even when it also displays the contents of those addresses. The default
5578 is @code{on}. For example, this is what a stack frame display looks like with
5579 @code{set print address on}:
5584 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
5586 530 if (lquote != def_lquote)
5590 @item set print address off
5591 Do not print addresses when displaying their contents. For example,
5592 this is the same stack frame displayed with @code{set print address off}:
5596 (@value{GDBP}) set print addr off
5598 #0 set_quotes (lq="<<", rq=">>") at input.c:530
5599 530 if (lquote != def_lquote)
5603 You can use @samp{set print address off} to eliminate all machine
5604 dependent displays from the @value{GDBN} interface. For example, with
5605 @code{print address off}, you should get the same text for backtraces on
5606 all machines---whether or not they involve pointer arguments.
5609 @item show print address
5610 Show whether or not addresses are to be printed.
5613 When @value{GDBN} prints a symbolic address, it normally prints the
5614 closest earlier symbol plus an offset. If that symbol does not uniquely
5615 identify the address (for example, it is a name whose scope is a single
5616 source file), you may need to clarify. One way to do this is with
5617 @code{info line}, for example @samp{info line *0x4537}. Alternately,
5618 you can set @value{GDBN} to print the source file and line number when
5619 it prints a symbolic address:
5622 @item set print symbol-filename on
5623 @cindex source file and line of a symbol
5624 @cindex symbol, source file and line
5625 Tell @value{GDBN} to print the source file name and line number of a
5626 symbol in the symbolic form of an address.
5628 @item set print symbol-filename off
5629 Do not print source file name and line number of a symbol. This is the
5632 @item show print symbol-filename
5633 Show whether or not @value{GDBN} will print the source file name and
5634 line number of a symbol in the symbolic form of an address.
5637 Another situation where it is helpful to show symbol filenames and line
5638 numbers is when disassembling code; @value{GDBN} shows you the line
5639 number and source file that corresponds to each instruction.
5641 Also, you may wish to see the symbolic form only if the address being
5642 printed is reasonably close to the closest earlier symbol:
5645 @item set print max-symbolic-offset @var{max-offset}
5646 @cindex maximum value for offset of closest symbol
5647 Tell @value{GDBN} to only display the symbolic form of an address if the
5648 offset between the closest earlier symbol and the address is less than
5649 @var{max-offset}. The default is 0, which tells @value{GDBN}
5650 to always print the symbolic form of an address if any symbol precedes it.
5652 @item show print max-symbolic-offset
5653 Ask how large the maximum offset is that @value{GDBN} prints in a
5657 @cindex wild pointer, interpreting
5658 @cindex pointer, finding referent
5659 If you have a pointer and you are not sure where it points, try
5660 @samp{set print symbol-filename on}. Then you can determine the name
5661 and source file location of the variable where it points, using
5662 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
5663 For example, here @value{GDBN} shows that a variable @code{ptt} points
5664 at another variable @code{t}, defined in @file{hi2.c}:
5667 (@value{GDBP}) set print symbol-filename on
5668 (@value{GDBP}) p/a ptt
5669 $4 = 0xe008 <t in hi2.c>
5673 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
5674 does not show the symbol name and filename of the referent, even with
5675 the appropriate @code{set print} options turned on.
5678 Other settings control how different kinds of objects are printed:
5681 @item set print array
5682 @itemx set print array on
5683 @cindex pretty print arrays
5684 Pretty print arrays. This format is more convenient to read,
5685 but uses more space. The default is off.
5687 @item set print array off
5688 Return to compressed format for arrays.
5690 @item show print array
5691 Show whether compressed or pretty format is selected for displaying
5694 @item set print elements @var{number-of-elements}
5695 @cindex number of array elements to print
5696 @cindex limit on number of printed array elements
5697 Set a limit on how many elements of an array @value{GDBN} will print.
5698 If @value{GDBN} is printing a large array, it stops printing after it has
5699 printed the number of elements set by the @code{set print elements} command.
5700 This limit also applies to the display of strings.
5701 When @value{GDBN} starts, this limit is set to 200.
5702 Setting @var{number-of-elements} to zero means that the printing is unlimited.
5704 @item show print elements
5705 Display the number of elements of a large array that @value{GDBN} will print.
5706 If the number is 0, then the printing is unlimited.
5708 @item set print repeats
5709 @cindex repeated array elements
5710 Set the threshold for suppressing display of repeated array
5711 elelments. When the number of consecutive identical elements of an
5712 array exceeds the threshold, @value{GDBN} prints the string
5713 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
5714 identical repetitions, instead of displaying the identical elements
5715 themselves. Setting the threshold to zero will cause all elements to
5716 be individually printed. The default threshold is 10.
5718 @item show print repeats
5719 Display the current threshold for printing repeated identical
5722 @item set print null-stop
5723 @cindex @sc{null} elements in arrays
5724 Cause @value{GDBN} to stop printing the characters of an array when the first
5725 @sc{null} is encountered. This is useful when large arrays actually
5726 contain only short strings.
5729 @item show print null-stop
5730 Show whether @value{GDBN} stops printing an array on the first
5731 @sc{null} character.
5733 @item set print pretty on
5734 @cindex print structures in indented form
5735 @cindex indentation in structure display
5736 Cause @value{GDBN} to print structures in an indented format with one member
5737 per line, like this:
5752 @item set print pretty off
5753 Cause @value{GDBN} to print structures in a compact format, like this:
5757 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
5758 meat = 0x54 "Pork"@}
5763 This is the default format.
5765 @item show print pretty
5766 Show which format @value{GDBN} is using to print structures.
5768 @item set print sevenbit-strings on
5769 @cindex eight-bit characters in strings
5770 @cindex octal escapes in strings
5771 Print using only seven-bit characters; if this option is set,
5772 @value{GDBN} displays any eight-bit characters (in strings or
5773 character values) using the notation @code{\}@var{nnn}. This setting is
5774 best if you are working in English (@sc{ascii}) and you use the
5775 high-order bit of characters as a marker or ``meta'' bit.
5777 @item set print sevenbit-strings off
5778 Print full eight-bit characters. This allows the use of more
5779 international character sets, and is the default.
5781 @item show print sevenbit-strings
5782 Show whether or not @value{GDBN} is printing only seven-bit characters.
5784 @item set print union on
5785 @cindex unions in structures, printing
5786 Tell @value{GDBN} to print unions which are contained in structures
5787 and other unions. This is the default setting.
5789 @item set print union off
5790 Tell @value{GDBN} not to print unions which are contained in
5791 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
5794 @item show print union
5795 Ask @value{GDBN} whether or not it will print unions which are contained in
5796 structures and other unions.
5798 For example, given the declarations
5801 typedef enum @{Tree, Bug@} Species;
5802 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
5803 typedef enum @{Caterpillar, Cocoon, Butterfly@}
5814 struct thing foo = @{Tree, @{Acorn@}@};
5818 with @code{set print union on} in effect @samp{p foo} would print
5821 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
5825 and with @code{set print union off} in effect it would print
5828 $1 = @{it = Tree, form = @{...@}@}
5832 @code{set print union} affects programs written in C-like languages
5838 These settings are of interest when debugging C@t{++} programs:
5841 @cindex demangling C@t{++} names
5842 @item set print demangle
5843 @itemx set print demangle on
5844 Print C@t{++} names in their source form rather than in the encoded
5845 (``mangled'') form passed to the assembler and linker for type-safe
5846 linkage. The default is on.
5848 @item show print demangle
5849 Show whether C@t{++} names are printed in mangled or demangled form.
5851 @item set print asm-demangle
5852 @itemx set print asm-demangle on
5853 Print C@t{++} names in their source form rather than their mangled form, even
5854 in assembler code printouts such as instruction disassemblies.
5857 @item show print asm-demangle
5858 Show whether C@t{++} names in assembly listings are printed in mangled
5861 @cindex C@t{++} symbol decoding style
5862 @cindex symbol decoding style, C@t{++}
5863 @kindex set demangle-style
5864 @item set demangle-style @var{style}
5865 Choose among several encoding schemes used by different compilers to
5866 represent C@t{++} names. The choices for @var{style} are currently:
5870 Allow @value{GDBN} to choose a decoding style by inspecting your program.
5873 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
5874 This is the default.
5877 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
5880 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
5883 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
5884 @strong{Warning:} this setting alone is not sufficient to allow
5885 debugging @code{cfront}-generated executables. @value{GDBN} would
5886 require further enhancement to permit that.
5889 If you omit @var{style}, you will see a list of possible formats.
5891 @item show demangle-style
5892 Display the encoding style currently in use for decoding C@t{++} symbols.
5894 @item set print object
5895 @itemx set print object on
5896 @cindex derived type of an object, printing
5897 @cindex display derived types
5898 When displaying a pointer to an object, identify the @emph{actual}
5899 (derived) type of the object rather than the @emph{declared} type, using
5900 the virtual function table.
5902 @item set print object off
5903 Display only the declared type of objects, without reference to the
5904 virtual function table. This is the default setting.
5906 @item show print object
5907 Show whether actual, or declared, object types are displayed.
5909 @item set print static-members
5910 @itemx set print static-members on
5911 @cindex static members of C@t{++} objects
5912 Print static members when displaying a C@t{++} object. The default is on.
5914 @item set print static-members off
5915 Do not print static members when displaying a C@t{++} object.
5917 @item show print static-members
5918 Show whether C@t{++} static members are printed or not.
5920 @item set print pascal_static-members
5921 @itemx set print pascal_static-members on
5922 @cindex static members of Pacal objects
5923 @cindex Pacal objects, static members display
5924 Print static members when displaying a Pascal object. The default is on.
5926 @item set print pascal_static-members off
5927 Do not print static members when displaying a Pascal object.
5929 @item show print pascal_static-members
5930 Show whether Pascal static members are printed or not.
5932 @c These don't work with HP ANSI C++ yet.
5933 @item set print vtbl
5934 @itemx set print vtbl on
5935 @cindex pretty print C@t{++} virtual function tables
5936 @cindex virtual functions (C@t{++}) display
5937 @cindex VTBL display
5938 Pretty print C@t{++} virtual function tables. The default is off.
5939 (The @code{vtbl} commands do not work on programs compiled with the HP
5940 ANSI C@t{++} compiler (@code{aCC}).)
5942 @item set print vtbl off
5943 Do not pretty print C@t{++} virtual function tables.
5945 @item show print vtbl
5946 Show whether C@t{++} virtual function tables are pretty printed, or not.
5950 @section Value history
5952 @cindex value history
5953 @cindex history of values printed by @value{GDBN}
5954 Values printed by the @code{print} command are saved in the @value{GDBN}
5955 @dfn{value history}. This allows you to refer to them in other expressions.
5956 Values are kept until the symbol table is re-read or discarded
5957 (for example with the @code{file} or @code{symbol-file} commands).
5958 When the symbol table changes, the value history is discarded,
5959 since the values may contain pointers back to the types defined in the
5964 @cindex history number
5965 The values printed are given @dfn{history numbers} by which you can
5966 refer to them. These are successive integers starting with one.
5967 @code{print} shows you the history number assigned to a value by
5968 printing @samp{$@var{num} = } before the value; here @var{num} is the
5971 To refer to any previous value, use @samp{$} followed by the value's
5972 history number. The way @code{print} labels its output is designed to
5973 remind you of this. Just @code{$} refers to the most recent value in
5974 the history, and @code{$$} refers to the value before that.
5975 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
5976 is the value just prior to @code{$$}, @code{$$1} is equivalent to
5977 @code{$$}, and @code{$$0} is equivalent to @code{$}.
5979 For example, suppose you have just printed a pointer to a structure and
5980 want to see the contents of the structure. It suffices to type
5986 If you have a chain of structures where the component @code{next} points
5987 to the next one, you can print the contents of the next one with this:
5994 You can print successive links in the chain by repeating this
5995 command---which you can do by just typing @key{RET}.
5997 Note that the history records values, not expressions. If the value of
5998 @code{x} is 4 and you type these commands:
6006 then the value recorded in the value history by the @code{print} command
6007 remains 4 even though the value of @code{x} has changed.
6012 Print the last ten values in the value history, with their item numbers.
6013 This is like @samp{p@ $$9} repeated ten times, except that @code{show
6014 values} does not change the history.
6016 @item show values @var{n}
6017 Print ten history values centered on history item number @var{n}.
6020 Print ten history values just after the values last printed. If no more
6021 values are available, @code{show values +} produces no display.
6024 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
6025 same effect as @samp{show values +}.
6027 @node Convenience Vars
6028 @section Convenience variables
6030 @cindex convenience variables
6031 @cindex user-defined variables
6032 @value{GDBN} provides @dfn{convenience variables} that you can use within
6033 @value{GDBN} to hold on to a value and refer to it later. These variables
6034 exist entirely within @value{GDBN}; they are not part of your program, and
6035 setting a convenience variable has no direct effect on further execution
6036 of your program. That is why you can use them freely.
6038 Convenience variables are prefixed with @samp{$}. Any name preceded by
6039 @samp{$} can be used for a convenience variable, unless it is one of
6040 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
6041 (Value history references, in contrast, are @emph{numbers} preceded
6042 by @samp{$}. @xref{Value History, ,Value history}.)
6044 You can save a value in a convenience variable with an assignment
6045 expression, just as you would set a variable in your program.
6049 set $foo = *object_ptr
6053 would save in @code{$foo} the value contained in the object pointed to by
6056 Using a convenience variable for the first time creates it, but its
6057 value is @code{void} until you assign a new value. You can alter the
6058 value with another assignment at any time.
6060 Convenience variables have no fixed types. You can assign a convenience
6061 variable any type of value, including structures and arrays, even if
6062 that variable already has a value of a different type. The convenience
6063 variable, when used as an expression, has the type of its current value.
6066 @kindex show convenience
6067 @cindex show all user variables
6068 @item show convenience
6069 Print a list of convenience variables used so far, and their values.
6070 Abbreviated @code{show conv}.
6073 One of the ways to use a convenience variable is as a counter to be
6074 incremented or a pointer to be advanced. For example, to print
6075 a field from successive elements of an array of structures:
6079 print bar[$i++]->contents
6083 Repeat that command by typing @key{RET}.
6085 Some convenience variables are created automatically by @value{GDBN} and given
6086 values likely to be useful.
6089 @vindex $_@r{, convenience variable}
6091 The variable @code{$_} is automatically set by the @code{x} command to
6092 the last address examined (@pxref{Memory, ,Examining memory}). Other
6093 commands which provide a default address for @code{x} to examine also
6094 set @code{$_} to that address; these commands include @code{info line}
6095 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
6096 except when set by the @code{x} command, in which case it is a pointer
6097 to the type of @code{$__}.
6099 @vindex $__@r{, convenience variable}
6101 The variable @code{$__} is automatically set by the @code{x} command
6102 to the value found in the last address examined. Its type is chosen
6103 to match the format in which the data was printed.
6106 @vindex $_exitcode@r{, convenience variable}
6107 The variable @code{$_exitcode} is automatically set to the exit code when
6108 the program being debugged terminates.
6111 On HP-UX systems, if you refer to a function or variable name that
6112 begins with a dollar sign, @value{GDBN} searches for a user or system
6113 name first, before it searches for a convenience variable.
6119 You can refer to machine register contents, in expressions, as variables
6120 with names starting with @samp{$}. The names of registers are different
6121 for each machine; use @code{info registers} to see the names used on
6125 @kindex info registers
6126 @item info registers
6127 Print the names and values of all registers except floating-point
6128 and vector registers (in the selected stack frame).
6130 @kindex info all-registers
6131 @cindex floating point registers
6132 @item info all-registers
6133 Print the names and values of all registers, including floating-point
6134 and vector registers (in the selected stack frame).
6136 @item info registers @var{regname} @dots{}
6137 Print the @dfn{relativized} value of each specified register @var{regname}.
6138 As discussed in detail below, register values are normally relative to
6139 the selected stack frame. @var{regname} may be any register name valid on
6140 the machine you are using, with or without the initial @samp{$}.
6143 @cindex stack pointer register
6144 @cindex program counter register
6145 @cindex process status register
6146 @cindex frame pointer register
6147 @cindex standard registers
6148 @value{GDBN} has four ``standard'' register names that are available (in
6149 expressions) on most machines---whenever they do not conflict with an
6150 architecture's canonical mnemonics for registers. The register names
6151 @code{$pc} and @code{$sp} are used for the program counter register and
6152 the stack pointer. @code{$fp} is used for a register that contains a
6153 pointer to the current stack frame, and @code{$ps} is used for a
6154 register that contains the processor status. For example,
6155 you could print the program counter in hex with
6162 or print the instruction to be executed next with
6169 or add four to the stack pointer@footnote{This is a way of removing
6170 one word from the stack, on machines where stacks grow downward in
6171 memory (most machines, nowadays). This assumes that the innermost
6172 stack frame is selected; setting @code{$sp} is not allowed when other
6173 stack frames are selected. To pop entire frames off the stack,
6174 regardless of machine architecture, use @code{return};
6175 see @ref{Returning, ,Returning from a function}.} with
6181 Whenever possible, these four standard register names are available on
6182 your machine even though the machine has different canonical mnemonics,
6183 so long as there is no conflict. The @code{info registers} command
6184 shows the canonical names. For example, on the SPARC, @code{info
6185 registers} displays the processor status register as @code{$psr} but you
6186 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
6187 is an alias for the @sc{eflags} register.
6189 @value{GDBN} always considers the contents of an ordinary register as an
6190 integer when the register is examined in this way. Some machines have
6191 special registers which can hold nothing but floating point; these
6192 registers are considered to have floating point values. There is no way
6193 to refer to the contents of an ordinary register as floating point value
6194 (although you can @emph{print} it as a floating point value with
6195 @samp{print/f $@var{regname}}).
6197 Some registers have distinct ``raw'' and ``virtual'' data formats. This
6198 means that the data format in which the register contents are saved by
6199 the operating system is not the same one that your program normally
6200 sees. For example, the registers of the 68881 floating point
6201 coprocessor are always saved in ``extended'' (raw) format, but all C
6202 programs expect to work with ``double'' (virtual) format. In such
6203 cases, @value{GDBN} normally works with the virtual format only (the format
6204 that makes sense for your program), but the @code{info registers} command
6205 prints the data in both formats.
6207 Normally, register values are relative to the selected stack frame
6208 (@pxref{Selection, ,Selecting a frame}). This means that you get the
6209 value that the register would contain if all stack frames farther in
6210 were exited and their saved registers restored. In order to see the
6211 true contents of hardware registers, you must select the innermost
6212 frame (with @samp{frame 0}).
6214 However, @value{GDBN} must deduce where registers are saved, from the machine
6215 code generated by your compiler. If some registers are not saved, or if
6216 @value{GDBN} is unable to locate the saved registers, the selected stack
6217 frame makes no difference.
6219 @node Floating Point Hardware
6220 @section Floating point hardware
6221 @cindex floating point
6223 Depending on the configuration, @value{GDBN} may be able to give
6224 you more information about the status of the floating point hardware.
6229 Display hardware-dependent information about the floating
6230 point unit. The exact contents and layout vary depending on the
6231 floating point chip. Currently, @samp{info float} is supported on
6232 the ARM and x86 machines.
6236 @section Vector Unit
6239 Depending on the configuration, @value{GDBN} may be able to give you
6240 more information about the status of the vector unit.
6245 Display information about the vector unit. The exact contents and
6246 layout vary depending on the hardware.
6249 @node OS Information
6250 @section Operating system auxiliary information
6251 @cindex OS information
6253 @value{GDBN} provides interfaces to useful OS facilities that can help
6254 you debug your program.
6256 @cindex @code{ptrace} system call
6257 @cindex @code{struct user} contents
6258 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
6259 machines), it interfaces with the inferior via the @code{ptrace}
6260 system call. The operating system creates a special sata structure,
6261 called @code{struct user}, for this interface. You can use the
6262 command @code{info udot} to display the contents of this data
6268 Display the contents of the @code{struct user} maintained by the OS
6269 kernel for the program being debugged. @value{GDBN} displays the
6270 contents of @code{struct user} as a list of hex numbers, similar to
6271 the @code{examine} command.
6274 @cindex auxiliary vector
6275 @cindex vector, auxiliary
6276 Some operating systems supply an @dfn{auxiliary vector} to programs at
6277 startup. This is akin to the arguments and environment that you
6278 specify for a program, but contains a system-dependent variety of
6279 binary values that tell system libraries important details about the
6280 hardware, operating system, and process. Each value's purpose is
6281 identified by an integer tag; the meanings are well-known but system-specific.
6282 Depending on the configuration and operating system facilities,
6283 @value{GDBN} may be able to show you this information. For remote
6284 targets, this functionality may further depend on the remote stub's
6285 support of the @samp{qPart:auxv:read} packet, see @ref{Remote
6286 configuration, auxiliary vector}.
6291 Display the auxiliary vector of the inferior, which can be either a
6292 live process or a core dump file. @value{GDBN} prints each tag value
6293 numerically, and also shows names and text descriptions for recognized
6294 tags. Some values in the vector are numbers, some bit masks, and some
6295 pointers to strings or other data. @value{GDBN} displays each value in the
6296 most appropriate form for a recognized tag, and in hexadecimal for
6297 an unrecognized tag.
6301 @node Memory Region Attributes
6302 @section Memory region attributes
6303 @cindex memory region attributes
6305 @dfn{Memory region attributes} allow you to describe special handling
6306 required by regions of your target's memory. @value{GDBN} uses attributes
6307 to determine whether to allow certain types of memory accesses; whether to
6308 use specific width accesses; and whether to cache target memory.
6310 Defined memory regions can be individually enabled and disabled. When a
6311 memory region is disabled, @value{GDBN} uses the default attributes when
6312 accessing memory in that region. Similarly, if no memory regions have
6313 been defined, @value{GDBN} uses the default attributes when accessing
6316 When a memory region is defined, it is given a number to identify it;
6317 to enable, disable, or remove a memory region, you specify that number.
6321 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
6322 Define a memory region bounded by @var{lower} and @var{upper} with
6323 attributes @var{attributes}@dots{}, and add it to the list of regions
6324 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
6325 case: it is treated as the the target's maximum memory address.
6326 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
6329 @item delete mem @var{nums}@dots{}
6330 Remove memory regions @var{nums}@dots{} from the list of regions
6331 monitored by @value{GDBN}.
6334 @item disable mem @var{nums}@dots{}
6335 Disable monitoring of memory regions @var{nums}@dots{}.
6336 A disabled memory region is not forgotten.
6337 It may be enabled again later.
6340 @item enable mem @var{nums}@dots{}
6341 Enable monitoring of memory regions @var{nums}@dots{}.
6345 Print a table of all defined memory regions, with the following columns
6349 @item Memory Region Number
6350 @item Enabled or Disabled.
6351 Enabled memory regions are marked with @samp{y}.
6352 Disabled memory regions are marked with @samp{n}.
6355 The address defining the inclusive lower bound of the memory region.
6358 The address defining the exclusive upper bound of the memory region.
6361 The list of attributes set for this memory region.
6366 @subsection Attributes
6368 @subsubsection Memory Access Mode
6369 The access mode attributes set whether @value{GDBN} may make read or
6370 write accesses to a memory region.
6372 While these attributes prevent @value{GDBN} from performing invalid
6373 memory accesses, they do nothing to prevent the target system, I/O DMA,
6374 etc. from accessing memory.
6378 Memory is read only.
6380 Memory is write only.
6382 Memory is read/write. This is the default.
6385 @subsubsection Memory Access Size
6386 The acccess size attributes tells @value{GDBN} to use specific sized
6387 accesses in the memory region. Often memory mapped device registers
6388 require specific sized accesses. If no access size attribute is
6389 specified, @value{GDBN} may use accesses of any size.
6393 Use 8 bit memory accesses.
6395 Use 16 bit memory accesses.
6397 Use 32 bit memory accesses.
6399 Use 64 bit memory accesses.
6402 @c @subsubsection Hardware/Software Breakpoints
6403 @c The hardware/software breakpoint attributes set whether @value{GDBN}
6404 @c will use hardware or software breakpoints for the internal breakpoints
6405 @c used by the step, next, finish, until, etc. commands.
6409 @c Always use hardware breakpoints
6410 @c @item swbreak (default)
6413 @subsubsection Data Cache
6414 The data cache attributes set whether @value{GDBN} will cache target
6415 memory. While this generally improves performance by reducing debug
6416 protocol overhead, it can lead to incorrect results because @value{GDBN}
6417 does not know about volatile variables or memory mapped device
6422 Enable @value{GDBN} to cache target memory.
6424 Disable @value{GDBN} from caching target memory. This is the default.
6427 @c @subsubsection Memory Write Verification
6428 @c The memory write verification attributes set whether @value{GDBN}
6429 @c will re-reads data after each write to verify the write was successful.
6433 @c @item noverify (default)
6436 @node Dump/Restore Files
6437 @section Copy between memory and a file
6438 @cindex dump/restore files
6439 @cindex append data to a file
6440 @cindex dump data to a file
6441 @cindex restore data from a file
6443 You can use the commands @code{dump}, @code{append}, and
6444 @code{restore} to copy data between target memory and a file. The
6445 @code{dump} and @code{append} commands write data to a file, and the
6446 @code{restore} command reads data from a file back into the inferior's
6447 memory. Files may be in binary, Motorola S-record, Intel hex, or
6448 Tektronix Hex format; however, @value{GDBN} can only append to binary
6454 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6455 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
6456 Dump the contents of memory from @var{start_addr} to @var{end_addr},
6457 or the value of @var{expr}, to @var{filename} in the given format.
6459 The @var{format} parameter may be any one of:
6466 Motorola S-record format.
6468 Tektronix Hex format.
6471 @value{GDBN} uses the same definitions of these formats as the
6472 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
6473 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
6477 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6478 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
6479 Append the contents of memory from @var{start_addr} to @var{end_addr},
6480 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
6481 (@value{GDBN} can only append data to files in raw binary form.)
6484 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
6485 Restore the contents of file @var{filename} into memory. The
6486 @code{restore} command can automatically recognize any known @sc{bfd}
6487 file format, except for raw binary. To restore a raw binary file you
6488 must specify the optional keyword @code{binary} after the filename.
6490 If @var{bias} is non-zero, its value will be added to the addresses
6491 contained in the file. Binary files always start at address zero, so
6492 they will be restored at address @var{bias}. Other bfd files have
6493 a built-in location; they will be restored at offset @var{bias}
6496 If @var{start} and/or @var{end} are non-zero, then only data between
6497 file offset @var{start} and file offset @var{end} will be restored.
6498 These offsets are relative to the addresses in the file, before
6499 the @var{bias} argument is applied.
6503 @node Core File Generation
6504 @section How to Produce a Core File from Your Program
6505 @cindex dump core from inferior
6507 A @dfn{core file} or @dfn{core dump} is a file that records the memory
6508 image of a running process and its process status (register values
6509 etc.). Its primary use is post-mortem debugging of a program that
6510 crashed while it ran outside a debugger. A program that crashes
6511 automatically produces a core file, unless this feature is disabled by
6512 the user. @xref{Files}, for information on invoking @value{GDBN} in
6513 the post-mortem debugging mode.
6515 Occasionally, you may wish to produce a core file of the program you
6516 are debugging in order to preserve a snapshot of its state.
6517 @value{GDBN} has a special command for that.
6521 @kindex generate-core-file
6522 @item generate-core-file [@var{file}]
6523 @itemx gcore [@var{file}]
6524 Produce a core dump of the inferior process. The optional argument
6525 @var{file} specifies the file name where to put the core dump. If not
6526 specified, the file name defaults to @file{core.@var{pid}}, where
6527 @var{pid} is the inferior process ID.
6529 Note that this command is implemented only for some systems (as of
6530 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
6533 @node Character Sets
6534 @section Character Sets
6535 @cindex character sets
6537 @cindex translating between character sets
6538 @cindex host character set
6539 @cindex target character set
6541 If the program you are debugging uses a different character set to
6542 represent characters and strings than the one @value{GDBN} uses itself,
6543 @value{GDBN} can automatically translate between the character sets for
6544 you. The character set @value{GDBN} uses we call the @dfn{host
6545 character set}; the one the inferior program uses we call the
6546 @dfn{target character set}.
6548 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
6549 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
6550 remote protocol (@pxref{Remote,Remote Debugging}) to debug a program
6551 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
6552 then the host character set is Latin-1, and the target character set is
6553 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
6554 target-charset EBCDIC-US}, then @value{GDBN} translates between
6555 @sc{ebcdic} and Latin 1 as you print character or string values, or use
6556 character and string literals in expressions.
6558 @value{GDBN} has no way to automatically recognize which character set
6559 the inferior program uses; you must tell it, using the @code{set
6560 target-charset} command, described below.
6562 Here are the commands for controlling @value{GDBN}'s character set
6566 @item set target-charset @var{charset}
6567 @kindex set target-charset
6568 Set the current target character set to @var{charset}. We list the
6569 character set names @value{GDBN} recognizes below, but if you type
6570 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6571 list the target character sets it supports.
6575 @item set host-charset @var{charset}
6576 @kindex set host-charset
6577 Set the current host character set to @var{charset}.
6579 By default, @value{GDBN} uses a host character set appropriate to the
6580 system it is running on; you can override that default using the
6581 @code{set host-charset} command.
6583 @value{GDBN} can only use certain character sets as its host character
6584 set. We list the character set names @value{GDBN} recognizes below, and
6585 indicate which can be host character sets, but if you type
6586 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6587 list the host character sets it supports.
6589 @item set charset @var{charset}
6591 Set the current host and target character sets to @var{charset}. As
6592 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
6593 @value{GDBN} will list the name of the character sets that can be used
6594 for both host and target.
6598 @kindex show charset
6599 Show the names of the current host and target charsets.
6601 @itemx show host-charset
6602 @kindex show host-charset
6603 Show the name of the current host charset.
6605 @itemx show target-charset
6606 @kindex show target-charset
6607 Show the name of the current target charset.
6611 @value{GDBN} currently includes support for the following character
6617 @cindex ASCII character set
6618 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
6622 @cindex ISO 8859-1 character set
6623 @cindex ISO Latin 1 character set
6624 The ISO Latin 1 character set. This extends @sc{ascii} with accented
6625 characters needed for French, German, and Spanish. @value{GDBN} can use
6626 this as its host character set.
6630 @cindex EBCDIC character set
6631 @cindex IBM1047 character set
6632 Variants of the @sc{ebcdic} character set, used on some of IBM's
6633 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
6634 @value{GDBN} cannot use these as its host character set.
6638 Note that these are all single-byte character sets. More work inside
6639 GDB is needed to support multi-byte or variable-width character
6640 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
6642 Here is an example of @value{GDBN}'s character set support in action.
6643 Assume that the following source code has been placed in the file
6644 @file{charset-test.c}:
6650 = @{72, 101, 108, 108, 111, 44, 32, 119,
6651 111, 114, 108, 100, 33, 10, 0@};
6652 char ibm1047_hello[]
6653 = @{200, 133, 147, 147, 150, 107, 64, 166,
6654 150, 153, 147, 132, 90, 37, 0@};
6658 printf ("Hello, world!\n");
6662 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
6663 containing the string @samp{Hello, world!} followed by a newline,
6664 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
6666 We compile the program, and invoke the debugger on it:
6669 $ gcc -g charset-test.c -o charset-test
6670 $ gdb -nw charset-test
6671 GNU gdb 2001-12-19-cvs
6672 Copyright 2001 Free Software Foundation, Inc.
6677 We can use the @code{show charset} command to see what character sets
6678 @value{GDBN} is currently using to interpret and display characters and
6682 (@value{GDBP}) show charset
6683 The current host and target character set is `ISO-8859-1'.
6687 For the sake of printing this manual, let's use @sc{ascii} as our
6688 initial character set:
6690 (@value{GDBP}) set charset ASCII
6691 (@value{GDBP}) show charset
6692 The current host and target character set is `ASCII'.
6696 Let's assume that @sc{ascii} is indeed the correct character set for our
6697 host system --- in other words, let's assume that if @value{GDBN} prints
6698 characters using the @sc{ascii} character set, our terminal will display
6699 them properly. Since our current target character set is also
6700 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
6703 (@value{GDBP}) print ascii_hello
6704 $1 = 0x401698 "Hello, world!\n"
6705 (@value{GDBP}) print ascii_hello[0]
6710 @value{GDBN} uses the target character set for character and string
6711 literals you use in expressions:
6714 (@value{GDBP}) print '+'
6719 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
6722 @value{GDBN} relies on the user to tell it which character set the
6723 target program uses. If we print @code{ibm1047_hello} while our target
6724 character set is still @sc{ascii}, we get jibberish:
6727 (@value{GDBP}) print ibm1047_hello
6728 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
6729 (@value{GDBP}) print ibm1047_hello[0]
6734 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
6735 @value{GDBN} tells us the character sets it supports:
6738 (@value{GDBP}) set target-charset
6739 ASCII EBCDIC-US IBM1047 ISO-8859-1
6740 (@value{GDBP}) set target-charset
6743 We can select @sc{ibm1047} as our target character set, and examine the
6744 program's strings again. Now the @sc{ascii} string is wrong, but
6745 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
6746 target character set, @sc{ibm1047}, to the host character set,
6747 @sc{ascii}, and they display correctly:
6750 (@value{GDBP}) set target-charset IBM1047
6751 (@value{GDBP}) show charset
6752 The current host character set is `ASCII'.
6753 The current target character set is `IBM1047'.
6754 (@value{GDBP}) print ascii_hello
6755 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
6756 (@value{GDBP}) print ascii_hello[0]
6758 (@value{GDBP}) print ibm1047_hello
6759 $8 = 0x4016a8 "Hello, world!\n"
6760 (@value{GDBP}) print ibm1047_hello[0]
6765 As above, @value{GDBN} uses the target character set for character and
6766 string literals you use in expressions:
6769 (@value{GDBP}) print '+'
6774 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
6777 @node Caching Remote Data
6778 @section Caching Data of Remote Targets
6779 @cindex caching data of remote targets
6781 @value{GDBN} can cache data exchanged between the debugger and a
6782 remote target (@pxref{Remote}). Such caching generally improves
6783 performance, because it reduces the overhead of the remote protocol by
6784 bundling memory reads and writes into large chunks. Unfortunately,
6785 @value{GDBN} does not currently know anything about volatile
6786 registers, and thus data caching will produce incorrect results when
6787 volatile registers are in use.
6790 @kindex set remotecache
6791 @item set remotecache on
6792 @itemx set remotecache off
6793 Set caching state for remote targets. When @code{ON}, use data
6794 caching. By default, this option is @code{OFF}.
6796 @kindex show remotecache
6797 @item show remotecache
6798 Show the current state of data caching for remote targets.
6802 Print the information about the data cache performance. The
6803 information displayed includes: the dcache width and depth; and for
6804 each cache line, how many times it was referenced, and its data and
6805 state (dirty, bad, ok, etc.). This command is useful for debugging
6806 the data cache operation.
6811 @chapter C Preprocessor Macros
6813 Some languages, such as C and C@t{++}, provide a way to define and invoke
6814 ``preprocessor macros'' which expand into strings of tokens.
6815 @value{GDBN} can evaluate expressions containing macro invocations, show
6816 the result of macro expansion, and show a macro's definition, including
6817 where it was defined.
6819 You may need to compile your program specially to provide @value{GDBN}
6820 with information about preprocessor macros. Most compilers do not
6821 include macros in their debugging information, even when you compile
6822 with the @option{-g} flag. @xref{Compilation}.
6824 A program may define a macro at one point, remove that definition later,
6825 and then provide a different definition after that. Thus, at different
6826 points in the program, a macro may have different definitions, or have
6827 no definition at all. If there is a current stack frame, @value{GDBN}
6828 uses the macros in scope at that frame's source code line. Otherwise,
6829 @value{GDBN} uses the macros in scope at the current listing location;
6832 At the moment, @value{GDBN} does not support the @code{##}
6833 token-splicing operator, the @code{#} stringification operator, or
6834 variable-arity macros.
6836 Whenever @value{GDBN} evaluates an expression, it always expands any
6837 macro invocations present in the expression. @value{GDBN} also provides
6838 the following commands for working with macros explicitly.
6842 @kindex macro expand
6843 @cindex macro expansion, showing the results of preprocessor
6844 @cindex preprocessor macro expansion, showing the results of
6845 @cindex expanding preprocessor macros
6846 @item macro expand @var{expression}
6847 @itemx macro exp @var{expression}
6848 Show the results of expanding all preprocessor macro invocations in
6849 @var{expression}. Since @value{GDBN} simply expands macros, but does
6850 not parse the result, @var{expression} need not be a valid expression;
6851 it can be any string of tokens.
6854 @item macro expand-once @var{expression}
6855 @itemx macro exp1 @var{expression}
6856 @cindex expand macro once
6857 @i{(This command is not yet implemented.)} Show the results of
6858 expanding those preprocessor macro invocations that appear explicitly in
6859 @var{expression}. Macro invocations appearing in that expansion are
6860 left unchanged. This command allows you to see the effect of a
6861 particular macro more clearly, without being confused by further
6862 expansions. Since @value{GDBN} simply expands macros, but does not
6863 parse the result, @var{expression} need not be a valid expression; it
6864 can be any string of tokens.
6867 @cindex macro definition, showing
6868 @cindex definition, showing a macro's
6869 @item info macro @var{macro}
6870 Show the definition of the macro named @var{macro}, and describe the
6871 source location where that definition was established.
6873 @kindex macro define
6874 @cindex user-defined macros
6875 @cindex defining macros interactively
6876 @cindex macros, user-defined
6877 @item macro define @var{macro} @var{replacement-list}
6878 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
6879 @i{(This command is not yet implemented.)} Introduce a definition for a
6880 preprocessor macro named @var{macro}, invocations of which are replaced
6881 by the tokens given in @var{replacement-list}. The first form of this
6882 command defines an ``object-like'' macro, which takes no arguments; the
6883 second form defines a ``function-like'' macro, which takes the arguments
6884 given in @var{arglist}.
6886 A definition introduced by this command is in scope in every expression
6887 evaluated in @value{GDBN}, until it is removed with the @command{macro
6888 undef} command, described below. The definition overrides all
6889 definitions for @var{macro} present in the program being debugged, as
6890 well as any previous user-supplied definition.
6893 @item macro undef @var{macro}
6894 @i{(This command is not yet implemented.)} Remove any user-supplied
6895 definition for the macro named @var{macro}. This command only affects
6896 definitions provided with the @command{macro define} command, described
6897 above; it cannot remove definitions present in the program being
6902 @i{(This command is not yet implemented.)} List all the macros
6903 defined using the @code{macro define} command.
6906 @cindex macros, example of debugging with
6907 Here is a transcript showing the above commands in action. First, we
6908 show our source files:
6916 #define ADD(x) (M + x)
6921 printf ("Hello, world!\n");
6923 printf ("We're so creative.\n");
6925 printf ("Goodbye, world!\n");
6932 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
6933 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
6934 compiler includes information about preprocessor macros in the debugging
6938 $ gcc -gdwarf-2 -g3 sample.c -o sample
6942 Now, we start @value{GDBN} on our sample program:
6946 GNU gdb 2002-05-06-cvs
6947 Copyright 2002 Free Software Foundation, Inc.
6948 GDB is free software, @dots{}
6952 We can expand macros and examine their definitions, even when the
6953 program is not running. @value{GDBN} uses the current listing position
6954 to decide which macro definitions are in scope:
6957 (@value{GDBP}) list main
6960 5 #define ADD(x) (M + x)
6965 10 printf ("Hello, world!\n");
6967 12 printf ("We're so creative.\n");
6968 (@value{GDBP}) info macro ADD
6969 Defined at /home/jimb/gdb/macros/play/sample.c:5
6970 #define ADD(x) (M + x)
6971 (@value{GDBP}) info macro Q
6972 Defined at /home/jimb/gdb/macros/play/sample.h:1
6973 included at /home/jimb/gdb/macros/play/sample.c:2
6975 (@value{GDBP}) macro expand ADD(1)
6976 expands to: (42 + 1)
6977 (@value{GDBP}) macro expand-once ADD(1)
6978 expands to: once (M + 1)
6982 In the example above, note that @command{macro expand-once} expands only
6983 the macro invocation explicit in the original text --- the invocation of
6984 @code{ADD} --- but does not expand the invocation of the macro @code{M},
6985 which was introduced by @code{ADD}.
6987 Once the program is running, GDB uses the macro definitions in force at
6988 the source line of the current stack frame:
6991 (@value{GDBP}) break main
6992 Breakpoint 1 at 0x8048370: file sample.c, line 10.
6994 Starting program: /home/jimb/gdb/macros/play/sample
6996 Breakpoint 1, main () at sample.c:10
6997 10 printf ("Hello, world!\n");
7001 At line 10, the definition of the macro @code{N} at line 9 is in force:
7004 (@value{GDBP}) info macro N
7005 Defined at /home/jimb/gdb/macros/play/sample.c:9
7007 (@value{GDBP}) macro expand N Q M
7009 (@value{GDBP}) print N Q M
7014 As we step over directives that remove @code{N}'s definition, and then
7015 give it a new definition, @value{GDBN} finds the definition (or lack
7016 thereof) in force at each point:
7021 12 printf ("We're so creative.\n");
7022 (@value{GDBP}) info macro N
7023 The symbol `N' has no definition as a C/C++ preprocessor macro
7024 at /home/jimb/gdb/macros/play/sample.c:12
7027 14 printf ("Goodbye, world!\n");
7028 (@value{GDBP}) info macro N
7029 Defined at /home/jimb/gdb/macros/play/sample.c:13
7031 (@value{GDBP}) macro expand N Q M
7032 expands to: 1729 < 42
7033 (@value{GDBP}) print N Q M
7040 @chapter Tracepoints
7041 @c This chapter is based on the documentation written by Michael
7042 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
7045 In some applications, it is not feasible for the debugger to interrupt
7046 the program's execution long enough for the developer to learn
7047 anything helpful about its behavior. If the program's correctness
7048 depends on its real-time behavior, delays introduced by a debugger
7049 might cause the program to change its behavior drastically, or perhaps
7050 fail, even when the code itself is correct. It is useful to be able
7051 to observe the program's behavior without interrupting it.
7053 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
7054 specify locations in the program, called @dfn{tracepoints}, and
7055 arbitrary expressions to evaluate when those tracepoints are reached.
7056 Later, using the @code{tfind} command, you can examine the values
7057 those expressions had when the program hit the tracepoints. The
7058 expressions may also denote objects in memory---structures or arrays,
7059 for example---whose values @value{GDBN} should record; while visiting
7060 a particular tracepoint, you may inspect those objects as if they were
7061 in memory at that moment. However, because @value{GDBN} records these
7062 values without interacting with you, it can do so quickly and
7063 unobtrusively, hopefully not disturbing the program's behavior.
7065 The tracepoint facility is currently available only for remote
7066 targets. @xref{Targets}. In addition, your remote target must know how
7067 to collect trace data. This functionality is implemented in the remote
7068 stub; however, none of the stubs distributed with @value{GDBN} support
7069 tracepoints as of this writing.
7071 This chapter describes the tracepoint commands and features.
7075 * Analyze Collected Data::
7076 * Tracepoint Variables::
7079 @node Set Tracepoints
7080 @section Commands to Set Tracepoints
7082 Before running such a @dfn{trace experiment}, an arbitrary number of
7083 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
7084 tracepoint has a number assigned to it by @value{GDBN}. Like with
7085 breakpoints, tracepoint numbers are successive integers starting from
7086 one. Many of the commands associated with tracepoints take the
7087 tracepoint number as their argument, to identify which tracepoint to
7090 For each tracepoint, you can specify, in advance, some arbitrary set
7091 of data that you want the target to collect in the trace buffer when
7092 it hits that tracepoint. The collected data can include registers,
7093 local variables, or global data. Later, you can use @value{GDBN}
7094 commands to examine the values these data had at the time the
7097 This section describes commands to set tracepoints and associated
7098 conditions and actions.
7101 * Create and Delete Tracepoints::
7102 * Enable and Disable Tracepoints::
7103 * Tracepoint Passcounts::
7104 * Tracepoint Actions::
7105 * Listing Tracepoints::
7106 * Starting and Stopping Trace Experiment::
7109 @node Create and Delete Tracepoints
7110 @subsection Create and Delete Tracepoints
7113 @cindex set tracepoint
7116 The @code{trace} command is very similar to the @code{break} command.
7117 Its argument can be a source line, a function name, or an address in
7118 the target program. @xref{Set Breaks}. The @code{trace} command
7119 defines a tracepoint, which is a point in the target program where the
7120 debugger will briefly stop, collect some data, and then allow the
7121 program to continue. Setting a tracepoint or changing its commands
7122 doesn't take effect until the next @code{tstart} command; thus, you
7123 cannot change the tracepoint attributes once a trace experiment is
7126 Here are some examples of using the @code{trace} command:
7129 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
7131 (@value{GDBP}) @b{trace +2} // 2 lines forward
7133 (@value{GDBP}) @b{trace my_function} // first source line of function
7135 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
7137 (@value{GDBP}) @b{trace *0x2117c4} // an address
7141 You can abbreviate @code{trace} as @code{tr}.
7144 @cindex last tracepoint number
7145 @cindex recent tracepoint number
7146 @cindex tracepoint number
7147 The convenience variable @code{$tpnum} records the tracepoint number
7148 of the most recently set tracepoint.
7150 @kindex delete tracepoint
7151 @cindex tracepoint deletion
7152 @item delete tracepoint @r{[}@var{num}@r{]}
7153 Permanently delete one or more tracepoints. With no argument, the
7154 default is to delete all tracepoints.
7159 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
7161 (@value{GDBP}) @b{delete trace} // remove all tracepoints
7165 You can abbreviate this command as @code{del tr}.
7168 @node Enable and Disable Tracepoints
7169 @subsection Enable and Disable Tracepoints
7172 @kindex disable tracepoint
7173 @item disable tracepoint @r{[}@var{num}@r{]}
7174 Disable tracepoint @var{num}, or all tracepoints if no argument
7175 @var{num} is given. A disabled tracepoint will have no effect during
7176 the next trace experiment, but it is not forgotten. You can re-enable
7177 a disabled tracepoint using the @code{enable tracepoint} command.
7179 @kindex enable tracepoint
7180 @item enable tracepoint @r{[}@var{num}@r{]}
7181 Enable tracepoint @var{num}, or all tracepoints. The enabled
7182 tracepoints will become effective the next time a trace experiment is
7186 @node Tracepoint Passcounts
7187 @subsection Tracepoint Passcounts
7191 @cindex tracepoint pass count
7192 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
7193 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
7194 automatically stop a trace experiment. If a tracepoint's passcount is
7195 @var{n}, then the trace experiment will be automatically stopped on
7196 the @var{n}'th time that tracepoint is hit. If the tracepoint number
7197 @var{num} is not specified, the @code{passcount} command sets the
7198 passcount of the most recently defined tracepoint. If no passcount is
7199 given, the trace experiment will run until stopped explicitly by the
7205 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
7206 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
7208 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
7209 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
7210 (@value{GDBP}) @b{trace foo}
7211 (@value{GDBP}) @b{pass 3}
7212 (@value{GDBP}) @b{trace bar}
7213 (@value{GDBP}) @b{pass 2}
7214 (@value{GDBP}) @b{trace baz}
7215 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
7216 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
7217 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
7218 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
7222 @node Tracepoint Actions
7223 @subsection Tracepoint Action Lists
7227 @cindex tracepoint actions
7228 @item actions @r{[}@var{num}@r{]}
7229 This command will prompt for a list of actions to be taken when the
7230 tracepoint is hit. If the tracepoint number @var{num} is not
7231 specified, this command sets the actions for the one that was most
7232 recently defined (so that you can define a tracepoint and then say
7233 @code{actions} without bothering about its number). You specify the
7234 actions themselves on the following lines, one action at a time, and
7235 terminate the actions list with a line containing just @code{end}. So
7236 far, the only defined actions are @code{collect} and
7237 @code{while-stepping}.
7239 @cindex remove actions from a tracepoint
7240 To remove all actions from a tracepoint, type @samp{actions @var{num}}
7241 and follow it immediately with @samp{end}.
7244 (@value{GDBP}) @b{collect @var{data}} // collect some data
7246 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
7248 (@value{GDBP}) @b{end} // signals the end of actions.
7251 In the following example, the action list begins with @code{collect}
7252 commands indicating the things to be collected when the tracepoint is
7253 hit. Then, in order to single-step and collect additional data
7254 following the tracepoint, a @code{while-stepping} command is used,
7255 followed by the list of things to be collected while stepping. The
7256 @code{while-stepping} command is terminated by its own separate
7257 @code{end} command. Lastly, the action list is terminated by an
7261 (@value{GDBP}) @b{trace foo}
7262 (@value{GDBP}) @b{actions}
7263 Enter actions for tracepoint 1, one per line:
7272 @kindex collect @r{(tracepoints)}
7273 @item collect @var{expr1}, @var{expr2}, @dots{}
7274 Collect values of the given expressions when the tracepoint is hit.
7275 This command accepts a comma-separated list of any valid expressions.
7276 In addition to global, static, or local variables, the following
7277 special arguments are supported:
7281 collect all registers
7284 collect all function arguments
7287 collect all local variables.
7290 You can give several consecutive @code{collect} commands, each one
7291 with a single argument, or one @code{collect} command with several
7292 arguments separated by commas: the effect is the same.
7294 The command @code{info scope} (@pxref{Symbols, info scope}) is
7295 particularly useful for figuring out what data to collect.
7297 @kindex while-stepping @r{(tracepoints)}
7298 @item while-stepping @var{n}
7299 Perform @var{n} single-step traces after the tracepoint, collecting
7300 new data at each step. The @code{while-stepping} command is
7301 followed by the list of what to collect while stepping (followed by
7302 its own @code{end} command):
7306 > collect $regs, myglobal
7312 You may abbreviate @code{while-stepping} as @code{ws} or
7316 @node Listing Tracepoints
7317 @subsection Listing Tracepoints
7320 @kindex info tracepoints
7322 @cindex information about tracepoints
7323 @item info tracepoints @r{[}@var{num}@r{]}
7324 Display information about the tracepoint @var{num}. If you don't specify
7325 a tracepoint number, displays information about all the tracepoints
7326 defined so far. For each tracepoint, the following information is
7333 whether it is enabled or disabled
7337 its passcount as given by the @code{passcount @var{n}} command
7339 its step count as given by the @code{while-stepping @var{n}} command
7341 where in the source files is the tracepoint set
7343 its action list as given by the @code{actions} command
7347 (@value{GDBP}) @b{info trace}
7348 Num Enb Address PassC StepC What
7349 1 y 0x002117c4 0 0 <gdb_asm>
7350 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
7351 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
7356 This command can be abbreviated @code{info tp}.
7359 @node Starting and Stopping Trace Experiment
7360 @subsection Starting and Stopping Trace Experiment
7364 @cindex start a new trace experiment
7365 @cindex collected data discarded
7367 This command takes no arguments. It starts the trace experiment, and
7368 begins collecting data. This has the side effect of discarding all
7369 the data collected in the trace buffer during the previous trace
7373 @cindex stop a running trace experiment
7375 This command takes no arguments. It ends the trace experiment, and
7376 stops collecting data.
7378 @strong{Note}: a trace experiment and data collection may stop
7379 automatically if any tracepoint's passcount is reached
7380 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
7383 @cindex status of trace data collection
7384 @cindex trace experiment, status of
7386 This command displays the status of the current trace data
7390 Here is an example of the commands we described so far:
7393 (@value{GDBP}) @b{trace gdb_c_test}
7394 (@value{GDBP}) @b{actions}
7395 Enter actions for tracepoint #1, one per line.
7396 > collect $regs,$locals,$args
7401 (@value{GDBP}) @b{tstart}
7402 [time passes @dots{}]
7403 (@value{GDBP}) @b{tstop}
7407 @node Analyze Collected Data
7408 @section Using the collected data
7410 After the tracepoint experiment ends, you use @value{GDBN} commands
7411 for examining the trace data. The basic idea is that each tracepoint
7412 collects a trace @dfn{snapshot} every time it is hit and another
7413 snapshot every time it single-steps. All these snapshots are
7414 consecutively numbered from zero and go into a buffer, and you can
7415 examine them later. The way you examine them is to @dfn{focus} on a
7416 specific trace snapshot. When the remote stub is focused on a trace
7417 snapshot, it will respond to all @value{GDBN} requests for memory and
7418 registers by reading from the buffer which belongs to that snapshot,
7419 rather than from @emph{real} memory or registers of the program being
7420 debugged. This means that @strong{all} @value{GDBN} commands
7421 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
7422 behave as if we were currently debugging the program state as it was
7423 when the tracepoint occurred. Any requests for data that are not in
7424 the buffer will fail.
7427 * tfind:: How to select a trace snapshot
7428 * tdump:: How to display all data for a snapshot
7429 * save-tracepoints:: How to save tracepoints for a future run
7433 @subsection @code{tfind @var{n}}
7436 @cindex select trace snapshot
7437 @cindex find trace snapshot
7438 The basic command for selecting a trace snapshot from the buffer is
7439 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
7440 counting from zero. If no argument @var{n} is given, the next
7441 snapshot is selected.
7443 Here are the various forms of using the @code{tfind} command.
7447 Find the first snapshot in the buffer. This is a synonym for
7448 @code{tfind 0} (since 0 is the number of the first snapshot).
7451 Stop debugging trace snapshots, resume @emph{live} debugging.
7454 Same as @samp{tfind none}.
7457 No argument means find the next trace snapshot.
7460 Find the previous trace snapshot before the current one. This permits
7461 retracing earlier steps.
7463 @item tfind tracepoint @var{num}
7464 Find the next snapshot associated with tracepoint @var{num}. Search
7465 proceeds forward from the last examined trace snapshot. If no
7466 argument @var{num} is given, it means find the next snapshot collected
7467 for the same tracepoint as the current snapshot.
7469 @item tfind pc @var{addr}
7470 Find the next snapshot associated with the value @var{addr} of the
7471 program counter. Search proceeds forward from the last examined trace
7472 snapshot. If no argument @var{addr} is given, it means find the next
7473 snapshot with the same value of PC as the current snapshot.
7475 @item tfind outside @var{addr1}, @var{addr2}
7476 Find the next snapshot whose PC is outside the given range of
7479 @item tfind range @var{addr1}, @var{addr2}
7480 Find the next snapshot whose PC is between @var{addr1} and
7481 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
7483 @item tfind line @r{[}@var{file}:@r{]}@var{n}
7484 Find the next snapshot associated with the source line @var{n}. If
7485 the optional argument @var{file} is given, refer to line @var{n} in
7486 that source file. Search proceeds forward from the last examined
7487 trace snapshot. If no argument @var{n} is given, it means find the
7488 next line other than the one currently being examined; thus saying
7489 @code{tfind line} repeatedly can appear to have the same effect as
7490 stepping from line to line in a @emph{live} debugging session.
7493 The default arguments for the @code{tfind} commands are specifically
7494 designed to make it easy to scan through the trace buffer. For
7495 instance, @code{tfind} with no argument selects the next trace
7496 snapshot, and @code{tfind -} with no argument selects the previous
7497 trace snapshot. So, by giving one @code{tfind} command, and then
7498 simply hitting @key{RET} repeatedly you can examine all the trace
7499 snapshots in order. Or, by saying @code{tfind -} and then hitting
7500 @key{RET} repeatedly you can examine the snapshots in reverse order.
7501 The @code{tfind line} command with no argument selects the snapshot
7502 for the next source line executed. The @code{tfind pc} command with
7503 no argument selects the next snapshot with the same program counter
7504 (PC) as the current frame. The @code{tfind tracepoint} command with
7505 no argument selects the next trace snapshot collected by the same
7506 tracepoint as the current one.
7508 In addition to letting you scan through the trace buffer manually,
7509 these commands make it easy to construct @value{GDBN} scripts that
7510 scan through the trace buffer and print out whatever collected data
7511 you are interested in. Thus, if we want to examine the PC, FP, and SP
7512 registers from each trace frame in the buffer, we can say this:
7515 (@value{GDBP}) @b{tfind start}
7516 (@value{GDBP}) @b{while ($trace_frame != -1)}
7517 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
7518 $trace_frame, $pc, $sp, $fp
7522 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
7523 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
7524 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
7525 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
7526 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
7527 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
7528 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
7529 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
7530 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
7531 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
7532 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
7535 Or, if we want to examine the variable @code{X} at each source line in
7539 (@value{GDBP}) @b{tfind start}
7540 (@value{GDBP}) @b{while ($trace_frame != -1)}
7541 > printf "Frame %d, X == %d\n", $trace_frame, X
7551 @subsection @code{tdump}
7553 @cindex dump all data collected at tracepoint
7554 @cindex tracepoint data, display
7556 This command takes no arguments. It prints all the data collected at
7557 the current trace snapshot.
7560 (@value{GDBP}) @b{trace 444}
7561 (@value{GDBP}) @b{actions}
7562 Enter actions for tracepoint #2, one per line:
7563 > collect $regs, $locals, $args, gdb_long_test
7566 (@value{GDBP}) @b{tstart}
7568 (@value{GDBP}) @b{tfind line 444}
7569 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
7571 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
7573 (@value{GDBP}) @b{tdump}
7574 Data collected at tracepoint 2, trace frame 1:
7575 d0 0xc4aa0085 -995491707
7579 d4 0x71aea3d 119204413
7584 a1 0x3000668 50333288
7587 a4 0x3000698 50333336
7589 fp 0x30bf3c 0x30bf3c
7590 sp 0x30bf34 0x30bf34
7592 pc 0x20b2c8 0x20b2c8
7596 p = 0x20e5b4 "gdb-test"
7603 gdb_long_test = 17 '\021'
7608 @node save-tracepoints
7609 @subsection @code{save-tracepoints @var{filename}}
7610 @kindex save-tracepoints
7611 @cindex save tracepoints for future sessions
7613 This command saves all current tracepoint definitions together with
7614 their actions and passcounts, into a file @file{@var{filename}}
7615 suitable for use in a later debugging session. To read the saved
7616 tracepoint definitions, use the @code{source} command (@pxref{Command
7619 @node Tracepoint Variables
7620 @section Convenience Variables for Tracepoints
7621 @cindex tracepoint variables
7622 @cindex convenience variables for tracepoints
7625 @vindex $trace_frame
7626 @item (int) $trace_frame
7627 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
7628 snapshot is selected.
7631 @item (int) $tracepoint
7632 The tracepoint for the current trace snapshot.
7635 @item (int) $trace_line
7636 The line number for the current trace snapshot.
7639 @item (char []) $trace_file
7640 The source file for the current trace snapshot.
7643 @item (char []) $trace_func
7644 The name of the function containing @code{$tracepoint}.
7647 Note: @code{$trace_file} is not suitable for use in @code{printf},
7648 use @code{output} instead.
7650 Here's a simple example of using these convenience variables for
7651 stepping through all the trace snapshots and printing some of their
7655 (@value{GDBP}) @b{tfind start}
7657 (@value{GDBP}) @b{while $trace_frame != -1}
7658 > output $trace_file
7659 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
7665 @chapter Debugging Programs That Use Overlays
7668 If your program is too large to fit completely in your target system's
7669 memory, you can sometimes use @dfn{overlays} to work around this
7670 problem. @value{GDBN} provides some support for debugging programs that
7674 * How Overlays Work:: A general explanation of overlays.
7675 * Overlay Commands:: Managing overlays in @value{GDBN}.
7676 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
7677 mapped by asking the inferior.
7678 * Overlay Sample Program:: A sample program using overlays.
7681 @node How Overlays Work
7682 @section How Overlays Work
7683 @cindex mapped overlays
7684 @cindex unmapped overlays
7685 @cindex load address, overlay's
7686 @cindex mapped address
7687 @cindex overlay area
7689 Suppose you have a computer whose instruction address space is only 64
7690 kilobytes long, but which has much more memory which can be accessed by
7691 other means: special instructions, segment registers, or memory
7692 management hardware, for example. Suppose further that you want to
7693 adapt a program which is larger than 64 kilobytes to run on this system.
7695 One solution is to identify modules of your program which are relatively
7696 independent, and need not call each other directly; call these modules
7697 @dfn{overlays}. Separate the overlays from the main program, and place
7698 their machine code in the larger memory. Place your main program in
7699 instruction memory, but leave at least enough space there to hold the
7700 largest overlay as well.
7702 Now, to call a function located in an overlay, you must first copy that
7703 overlay's machine code from the large memory into the space set aside
7704 for it in the instruction memory, and then jump to its entry point
7707 @c NB: In the below the mapped area's size is greater or equal to the
7708 @c size of all overlays. This is intentional to remind the developer
7709 @c that overlays don't necessarily need to be the same size.
7713 Data Instruction Larger
7714 Address Space Address Space Address Space
7715 +-----------+ +-----------+ +-----------+
7717 +-----------+ +-----------+ +-----------+<-- overlay 1
7718 | program | | main | .----| overlay 1 | load address
7719 | variables | | program | | +-----------+
7720 | and heap | | | | | |
7721 +-----------+ | | | +-----------+<-- overlay 2
7722 | | +-----------+ | | | load address
7723 +-----------+ | | | .-| overlay 2 |
7725 mapped --->+-----------+ | | +-----------+
7727 | overlay | <-' | | |
7728 | area | <---' +-----------+<-- overlay 3
7729 | | <---. | | load address
7730 +-----------+ `--| overlay 3 |
7737 @anchor{A code overlay}A code overlay
7741 The diagram (@pxref{A code overlay}) shows a system with separate data
7742 and instruction address spaces. To map an overlay, the program copies
7743 its code from the larger address space to the instruction address space.
7744 Since the overlays shown here all use the same mapped address, only one
7745 may be mapped at a time. For a system with a single address space for
7746 data and instructions, the diagram would be similar, except that the
7747 program variables and heap would share an address space with the main
7748 program and the overlay area.
7750 An overlay loaded into instruction memory and ready for use is called a
7751 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
7752 instruction memory. An overlay not present (or only partially present)
7753 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
7754 is its address in the larger memory. The mapped address is also called
7755 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
7756 called the @dfn{load memory address}, or @dfn{LMA}.
7758 Unfortunately, overlays are not a completely transparent way to adapt a
7759 program to limited instruction memory. They introduce a new set of
7760 global constraints you must keep in mind as you design your program:
7765 Before calling or returning to a function in an overlay, your program
7766 must make sure that overlay is actually mapped. Otherwise, the call or
7767 return will transfer control to the right address, but in the wrong
7768 overlay, and your program will probably crash.
7771 If the process of mapping an overlay is expensive on your system, you
7772 will need to choose your overlays carefully to minimize their effect on
7773 your program's performance.
7776 The executable file you load onto your system must contain each
7777 overlay's instructions, appearing at the overlay's load address, not its
7778 mapped address. However, each overlay's instructions must be relocated
7779 and its symbols defined as if the overlay were at its mapped address.
7780 You can use GNU linker scripts to specify different load and relocation
7781 addresses for pieces of your program; see @ref{Overlay Description,,,
7782 ld.info, Using ld: the GNU linker}.
7785 The procedure for loading executable files onto your system must be able
7786 to load their contents into the larger address space as well as the
7787 instruction and data spaces.
7791 The overlay system described above is rather simple, and could be
7792 improved in many ways:
7797 If your system has suitable bank switch registers or memory management
7798 hardware, you could use those facilities to make an overlay's load area
7799 contents simply appear at their mapped address in instruction space.
7800 This would probably be faster than copying the overlay to its mapped
7801 area in the usual way.
7804 If your overlays are small enough, you could set aside more than one
7805 overlay area, and have more than one overlay mapped at a time.
7808 You can use overlays to manage data, as well as instructions. In
7809 general, data overlays are even less transparent to your design than
7810 code overlays: whereas code overlays only require care when you call or
7811 return to functions, data overlays require care every time you access
7812 the data. Also, if you change the contents of a data overlay, you
7813 must copy its contents back out to its load address before you can copy a
7814 different data overlay into the same mapped area.
7819 @node Overlay Commands
7820 @section Overlay Commands
7822 To use @value{GDBN}'s overlay support, each overlay in your program must
7823 correspond to a separate section of the executable file. The section's
7824 virtual memory address and load memory address must be the overlay's
7825 mapped and load addresses. Identifying overlays with sections allows
7826 @value{GDBN} to determine the appropriate address of a function or
7827 variable, depending on whether the overlay is mapped or not.
7829 @value{GDBN}'s overlay commands all start with the word @code{overlay};
7830 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
7835 Disable @value{GDBN}'s overlay support. When overlay support is
7836 disabled, @value{GDBN} assumes that all functions and variables are
7837 always present at their mapped addresses. By default, @value{GDBN}'s
7838 overlay support is disabled.
7840 @item overlay manual
7841 @cindex manual overlay debugging
7842 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
7843 relies on you to tell it which overlays are mapped, and which are not,
7844 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
7845 commands described below.
7847 @item overlay map-overlay @var{overlay}
7848 @itemx overlay map @var{overlay}
7849 @cindex map an overlay
7850 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
7851 be the name of the object file section containing the overlay. When an
7852 overlay is mapped, @value{GDBN} assumes it can find the overlay's
7853 functions and variables at their mapped addresses. @value{GDBN} assumes
7854 that any other overlays whose mapped ranges overlap that of
7855 @var{overlay} are now unmapped.
7857 @item overlay unmap-overlay @var{overlay}
7858 @itemx overlay unmap @var{overlay}
7859 @cindex unmap an overlay
7860 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
7861 must be the name of the object file section containing the overlay.
7862 When an overlay is unmapped, @value{GDBN} assumes it can find the
7863 overlay's functions and variables at their load addresses.
7866 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
7867 consults a data structure the overlay manager maintains in the inferior
7868 to see which overlays are mapped. For details, see @ref{Automatic
7871 @item overlay load-target
7873 @cindex reloading the overlay table
7874 Re-read the overlay table from the inferior. Normally, @value{GDBN}
7875 re-reads the table @value{GDBN} automatically each time the inferior
7876 stops, so this command should only be necessary if you have changed the
7877 overlay mapping yourself using @value{GDBN}. This command is only
7878 useful when using automatic overlay debugging.
7880 @item overlay list-overlays
7882 @cindex listing mapped overlays
7883 Display a list of the overlays currently mapped, along with their mapped
7884 addresses, load addresses, and sizes.
7888 Normally, when @value{GDBN} prints a code address, it includes the name
7889 of the function the address falls in:
7892 (@value{GDBP}) print main
7893 $3 = @{int ()@} 0x11a0 <main>
7896 When overlay debugging is enabled, @value{GDBN} recognizes code in
7897 unmapped overlays, and prints the names of unmapped functions with
7898 asterisks around them. For example, if @code{foo} is a function in an
7899 unmapped overlay, @value{GDBN} prints it this way:
7902 (@value{GDBP}) overlay list
7903 No sections are mapped.
7904 (@value{GDBP}) print foo
7905 $5 = @{int (int)@} 0x100000 <*foo*>
7908 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
7912 (@value{GDBP}) overlay list
7913 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
7914 mapped at 0x1016 - 0x104a
7915 (@value{GDBP}) print foo
7916 $6 = @{int (int)@} 0x1016 <foo>
7919 When overlay debugging is enabled, @value{GDBN} can find the correct
7920 address for functions and variables in an overlay, whether or not the
7921 overlay is mapped. This allows most @value{GDBN} commands, like
7922 @code{break} and @code{disassemble}, to work normally, even on unmapped
7923 code. However, @value{GDBN}'s breakpoint support has some limitations:
7927 @cindex breakpoints in overlays
7928 @cindex overlays, setting breakpoints in
7929 You can set breakpoints in functions in unmapped overlays, as long as
7930 @value{GDBN} can write to the overlay at its load address.
7932 @value{GDBN} can not set hardware or simulator-based breakpoints in
7933 unmapped overlays. However, if you set a breakpoint at the end of your
7934 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
7935 you are using manual overlay management), @value{GDBN} will re-set its
7936 breakpoints properly.
7940 @node Automatic Overlay Debugging
7941 @section Automatic Overlay Debugging
7942 @cindex automatic overlay debugging
7944 @value{GDBN} can automatically track which overlays are mapped and which
7945 are not, given some simple co-operation from the overlay manager in the
7946 inferior. If you enable automatic overlay debugging with the
7947 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
7948 looks in the inferior's memory for certain variables describing the
7949 current state of the overlays.
7951 Here are the variables your overlay manager must define to support
7952 @value{GDBN}'s automatic overlay debugging:
7956 @item @code{_ovly_table}:
7957 This variable must be an array of the following structures:
7962 /* The overlay's mapped address. */
7965 /* The size of the overlay, in bytes. */
7968 /* The overlay's load address. */
7971 /* Non-zero if the overlay is currently mapped;
7973 unsigned long mapped;
7977 @item @code{_novlys}:
7978 This variable must be a four-byte signed integer, holding the total
7979 number of elements in @code{_ovly_table}.
7983 To decide whether a particular overlay is mapped or not, @value{GDBN}
7984 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
7985 @code{lma} members equal the VMA and LMA of the overlay's section in the
7986 executable file. When @value{GDBN} finds a matching entry, it consults
7987 the entry's @code{mapped} member to determine whether the overlay is
7990 In addition, your overlay manager may define a function called
7991 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
7992 will silently set a breakpoint there. If the overlay manager then
7993 calls this function whenever it has changed the overlay table, this
7994 will enable @value{GDBN} to accurately keep track of which overlays
7995 are in program memory, and update any breakpoints that may be set
7996 in overlays. This will allow breakpoints to work even if the
7997 overlays are kept in ROM or other non-writable memory while they
7998 are not being executed.
8000 @node Overlay Sample Program
8001 @section Overlay Sample Program
8002 @cindex overlay example program
8004 When linking a program which uses overlays, you must place the overlays
8005 at their load addresses, while relocating them to run at their mapped
8006 addresses. To do this, you must write a linker script (@pxref{Overlay
8007 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
8008 since linker scripts are specific to a particular host system, target
8009 architecture, and target memory layout, this manual cannot provide
8010 portable sample code demonstrating @value{GDBN}'s overlay support.
8012 However, the @value{GDBN} source distribution does contain an overlaid
8013 program, with linker scripts for a few systems, as part of its test
8014 suite. The program consists of the following files from
8015 @file{gdb/testsuite/gdb.base}:
8019 The main program file.
8021 A simple overlay manager, used by @file{overlays.c}.
8026 Overlay modules, loaded and used by @file{overlays.c}.
8029 Linker scripts for linking the test program on the @code{d10v-elf}
8030 and @code{m32r-elf} targets.
8033 You can build the test program using the @code{d10v-elf} GCC
8034 cross-compiler like this:
8037 $ d10v-elf-gcc -g -c overlays.c
8038 $ d10v-elf-gcc -g -c ovlymgr.c
8039 $ d10v-elf-gcc -g -c foo.c
8040 $ d10v-elf-gcc -g -c bar.c
8041 $ d10v-elf-gcc -g -c baz.c
8042 $ d10v-elf-gcc -g -c grbx.c
8043 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
8044 baz.o grbx.o -Wl,-Td10v.ld -o overlays
8047 The build process is identical for any other architecture, except that
8048 you must substitute the appropriate compiler and linker script for the
8049 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
8053 @chapter Using @value{GDBN} with Different Languages
8056 Although programming languages generally have common aspects, they are
8057 rarely expressed in the same manner. For instance, in ANSI C,
8058 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
8059 Modula-2, it is accomplished by @code{p^}. Values can also be
8060 represented (and displayed) differently. Hex numbers in C appear as
8061 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
8063 @cindex working language
8064 Language-specific information is built into @value{GDBN} for some languages,
8065 allowing you to express operations like the above in your program's
8066 native language, and allowing @value{GDBN} to output values in a manner
8067 consistent with the syntax of your program's native language. The
8068 language you use to build expressions is called the @dfn{working
8072 * Setting:: Switching between source languages
8073 * Show:: Displaying the language
8074 * Checks:: Type and range checks
8075 * Supported languages:: Supported languages
8076 * Unsupported languages:: Unsupported languages
8080 @section Switching between source languages
8082 There are two ways to control the working language---either have @value{GDBN}
8083 set it automatically, or select it manually yourself. You can use the
8084 @code{set language} command for either purpose. On startup, @value{GDBN}
8085 defaults to setting the language automatically. The working language is
8086 used to determine how expressions you type are interpreted, how values
8089 In addition to the working language, every source file that
8090 @value{GDBN} knows about has its own working language. For some object
8091 file formats, the compiler might indicate which language a particular
8092 source file is in. However, most of the time @value{GDBN} infers the
8093 language from the name of the file. The language of a source file
8094 controls whether C@t{++} names are demangled---this way @code{backtrace} can
8095 show each frame appropriately for its own language. There is no way to
8096 set the language of a source file from within @value{GDBN}, but you can
8097 set the language associated with a filename extension. @xref{Show, ,
8098 Displaying the language}.
8100 This is most commonly a problem when you use a program, such
8101 as @code{cfront} or @code{f2c}, that generates C but is written in
8102 another language. In that case, make the
8103 program use @code{#line} directives in its C output; that way
8104 @value{GDBN} will know the correct language of the source code of the original
8105 program, and will display that source code, not the generated C code.
8108 * Filenames:: Filename extensions and languages.
8109 * Manually:: Setting the working language manually
8110 * Automatically:: Having @value{GDBN} infer the source language
8114 @subsection List of filename extensions and languages
8116 If a source file name ends in one of the following extensions, then
8117 @value{GDBN} infers that its language is the one indicated.
8138 Objective-C source file
8145 Modula-2 source file
8149 Assembler source file. This actually behaves almost like C, but
8150 @value{GDBN} does not skip over function prologues when stepping.
8153 In addition, you may set the language associated with a filename
8154 extension. @xref{Show, , Displaying the language}.
8157 @subsection Setting the working language
8159 If you allow @value{GDBN} to set the language automatically,
8160 expressions are interpreted the same way in your debugging session and
8163 @kindex set language
8164 If you wish, you may set the language manually. To do this, issue the
8165 command @samp{set language @var{lang}}, where @var{lang} is the name of
8167 @code{c} or @code{modula-2}.
8168 For a list of the supported languages, type @samp{set language}.
8170 Setting the language manually prevents @value{GDBN} from updating the working
8171 language automatically. This can lead to confusion if you try
8172 to debug a program when the working language is not the same as the
8173 source language, when an expression is acceptable to both
8174 languages---but means different things. For instance, if the current
8175 source file were written in C, and @value{GDBN} was parsing Modula-2, a
8183 might not have the effect you intended. In C, this means to add
8184 @code{b} and @code{c} and place the result in @code{a}. The result
8185 printed would be the value of @code{a}. In Modula-2, this means to compare
8186 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
8189 @subsection Having @value{GDBN} infer the source language
8191 To have @value{GDBN} set the working language automatically, use
8192 @samp{set language local} or @samp{set language auto}. @value{GDBN}
8193 then infers the working language. That is, when your program stops in a
8194 frame (usually by encountering a breakpoint), @value{GDBN} sets the
8195 working language to the language recorded for the function in that
8196 frame. If the language for a frame is unknown (that is, if the function
8197 or block corresponding to the frame was defined in a source file that
8198 does not have a recognized extension), the current working language is
8199 not changed, and @value{GDBN} issues a warning.
8201 This may not seem necessary for most programs, which are written
8202 entirely in one source language. However, program modules and libraries
8203 written in one source language can be used by a main program written in
8204 a different source language. Using @samp{set language auto} in this
8205 case frees you from having to set the working language manually.
8208 @section Displaying the language
8210 The following commands help you find out which language is the
8211 working language, and also what language source files were written in.
8215 @kindex show language
8216 Display the current working language. This is the
8217 language you can use with commands such as @code{print} to
8218 build and compute expressions that may involve variables in your program.
8221 @kindex info frame@r{, show the source language}
8222 Display the source language for this frame. This language becomes the
8223 working language if you use an identifier from this frame.
8224 @xref{Frame Info, ,Information about a frame}, to identify the other
8225 information listed here.
8228 @kindex info source@r{, show the source language}
8229 Display the source language of this source file.
8230 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
8231 information listed here.
8234 In unusual circumstances, you may have source files with extensions
8235 not in the standard list. You can then set the extension associated
8236 with a language explicitly:
8239 @item set extension-language @var{ext} @var{language}
8240 @kindex set extension-language
8241 Tell @value{GDBN} that source files with extension @var{ext} are to be
8242 assumed as written in the source language @var{language}.
8244 @item info extensions
8245 @kindex info extensions
8246 List all the filename extensions and the associated languages.
8250 @section Type and range checking
8253 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
8254 checking are included, but they do not yet have any effect. This
8255 section documents the intended facilities.
8257 @c FIXME remove warning when type/range code added
8259 Some languages are designed to guard you against making seemingly common
8260 errors through a series of compile- and run-time checks. These include
8261 checking the type of arguments to functions and operators, and making
8262 sure mathematical overflows are caught at run time. Checks such as
8263 these help to ensure a program's correctness once it has been compiled
8264 by eliminating type mismatches, and providing active checks for range
8265 errors when your program is running.
8267 @value{GDBN} can check for conditions like the above if you wish.
8268 Although @value{GDBN} does not check the statements in your program,
8269 it can check expressions entered directly into @value{GDBN} for
8270 evaluation via the @code{print} command, for example. As with the
8271 working language, @value{GDBN} can also decide whether or not to check
8272 automatically based on your program's source language.
8273 @xref{Supported languages, ,Supported languages}, for the default
8274 settings of supported languages.
8277 * Type Checking:: An overview of type checking
8278 * Range Checking:: An overview of range checking
8281 @cindex type checking
8282 @cindex checks, type
8284 @subsection An overview of type checking
8286 Some languages, such as Modula-2, are strongly typed, meaning that the
8287 arguments to operators and functions have to be of the correct type,
8288 otherwise an error occurs. These checks prevent type mismatch
8289 errors from ever causing any run-time problems. For example,
8297 The second example fails because the @code{CARDINAL} 1 is not
8298 type-compatible with the @code{REAL} 2.3.
8300 For the expressions you use in @value{GDBN} commands, you can tell the
8301 @value{GDBN} type checker to skip checking;
8302 to treat any mismatches as errors and abandon the expression;
8303 or to only issue warnings when type mismatches occur,
8304 but evaluate the expression anyway. When you choose the last of
8305 these, @value{GDBN} evaluates expressions like the second example above, but
8306 also issues a warning.
8308 Even if you turn type checking off, there may be other reasons
8309 related to type that prevent @value{GDBN} from evaluating an expression.
8310 For instance, @value{GDBN} does not know how to add an @code{int} and
8311 a @code{struct foo}. These particular type errors have nothing to do
8312 with the language in use, and usually arise from expressions, such as
8313 the one described above, which make little sense to evaluate anyway.
8315 Each language defines to what degree it is strict about type. For
8316 instance, both Modula-2 and C require the arguments to arithmetical
8317 operators to be numbers. In C, enumerated types and pointers can be
8318 represented as numbers, so that they are valid arguments to mathematical
8319 operators. @xref{Supported languages, ,Supported languages}, for further
8320 details on specific languages.
8322 @value{GDBN} provides some additional commands for controlling the type checker:
8324 @kindex set check type
8325 @kindex show check type
8327 @item set check type auto
8328 Set type checking on or off based on the current working language.
8329 @xref{Supported languages, ,Supported languages}, for the default settings for
8332 @item set check type on
8333 @itemx set check type off
8334 Set type checking on or off, overriding the default setting for the
8335 current working language. Issue a warning if the setting does not
8336 match the language default. If any type mismatches occur in
8337 evaluating an expression while type checking is on, @value{GDBN} prints a
8338 message and aborts evaluation of the expression.
8340 @item set check type warn
8341 Cause the type checker to issue warnings, but to always attempt to
8342 evaluate the expression. Evaluating the expression may still
8343 be impossible for other reasons. For example, @value{GDBN} cannot add
8344 numbers and structures.
8347 Show the current setting of the type checker, and whether or not @value{GDBN}
8348 is setting it automatically.
8351 @cindex range checking
8352 @cindex checks, range
8353 @node Range Checking
8354 @subsection An overview of range checking
8356 In some languages (such as Modula-2), it is an error to exceed the
8357 bounds of a type; this is enforced with run-time checks. Such range
8358 checking is meant to ensure program correctness by making sure
8359 computations do not overflow, or indices on an array element access do
8360 not exceed the bounds of the array.
8362 For expressions you use in @value{GDBN} commands, you can tell
8363 @value{GDBN} to treat range errors in one of three ways: ignore them,
8364 always treat them as errors and abandon the expression, or issue
8365 warnings but evaluate the expression anyway.
8367 A range error can result from numerical overflow, from exceeding an
8368 array index bound, or when you type a constant that is not a member
8369 of any type. Some languages, however, do not treat overflows as an
8370 error. In many implementations of C, mathematical overflow causes the
8371 result to ``wrap around'' to lower values---for example, if @var{m} is
8372 the largest integer value, and @var{s} is the smallest, then
8375 @var{m} + 1 @result{} @var{s}
8378 This, too, is specific to individual languages, and in some cases
8379 specific to individual compilers or machines. @xref{Supported languages, ,
8380 Supported languages}, for further details on specific languages.
8382 @value{GDBN} provides some additional commands for controlling the range checker:
8384 @kindex set check range
8385 @kindex show check range
8387 @item set check range auto
8388 Set range checking on or off based on the current working language.
8389 @xref{Supported languages, ,Supported languages}, for the default settings for
8392 @item set check range on
8393 @itemx set check range off
8394 Set range checking on or off, overriding the default setting for the
8395 current working language. A warning is issued if the setting does not
8396 match the language default. If a range error occurs and range checking is on,
8397 then a message is printed and evaluation of the expression is aborted.
8399 @item set check range warn
8400 Output messages when the @value{GDBN} range checker detects a range error,
8401 but attempt to evaluate the expression anyway. Evaluating the
8402 expression may still be impossible for other reasons, such as accessing
8403 memory that the process does not own (a typical example from many Unix
8407 Show the current setting of the range checker, and whether or not it is
8408 being set automatically by @value{GDBN}.
8411 @node Supported languages
8412 @section Supported languages
8414 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
8415 assembly, Modula-2, and Ada.
8416 @c This is false ...
8417 Some @value{GDBN} features may be used in expressions regardless of the
8418 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
8419 and the @samp{@{type@}addr} construct (@pxref{Expressions,
8420 ,Expressions}) can be used with the constructs of any supported
8423 The following sections detail to what degree each source language is
8424 supported by @value{GDBN}. These sections are not meant to be language
8425 tutorials or references, but serve only as a reference guide to what the
8426 @value{GDBN} expression parser accepts, and what input and output
8427 formats should look like for different languages. There are many good
8428 books written on each of these languages; please look to these for a
8429 language reference or tutorial.
8433 * Objective-C:: Objective-C
8436 * Modula-2:: Modula-2
8441 @subsection C and C@t{++}
8443 @cindex C and C@t{++}
8444 @cindex expressions in C or C@t{++}
8446 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
8447 to both languages. Whenever this is the case, we discuss those languages
8451 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
8452 @cindex @sc{gnu} C@t{++}
8453 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
8454 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
8455 effectively, you must compile your C@t{++} programs with a supported
8456 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
8457 compiler (@code{aCC}).
8459 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
8460 format; if it doesn't work on your system, try the stabs+ debugging
8461 format. You can select those formats explicitly with the @code{g++}
8462 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
8463 @xref{Debugging Options,,Options for Debugging Your Program or @sc{gnu}
8464 CC, gcc.info, Using @sc{gnu} CC}.
8467 * C Operators:: C and C@t{++} operators
8468 * C Constants:: C and C@t{++} constants
8469 * C plus plus expressions:: C@t{++} expressions
8470 * C Defaults:: Default settings for C and C@t{++}
8471 * C Checks:: C and C@t{++} type and range checks
8472 * Debugging C:: @value{GDBN} and C
8473 * Debugging C plus plus:: @value{GDBN} features for C@t{++}
8477 @subsubsection C and C@t{++} operators
8479 @cindex C and C@t{++} operators
8481 Operators must be defined on values of specific types. For instance,
8482 @code{+} is defined on numbers, but not on structures. Operators are
8483 often defined on groups of types.
8485 For the purposes of C and C@t{++}, the following definitions hold:
8490 @emph{Integral types} include @code{int} with any of its storage-class
8491 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
8494 @emph{Floating-point types} include @code{float}, @code{double}, and
8495 @code{long double} (if supported by the target platform).
8498 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
8501 @emph{Scalar types} include all of the above.
8506 The following operators are supported. They are listed here
8507 in order of increasing precedence:
8511 The comma or sequencing operator. Expressions in a comma-separated list
8512 are evaluated from left to right, with the result of the entire
8513 expression being the last expression evaluated.
8516 Assignment. The value of an assignment expression is the value
8517 assigned. Defined on scalar types.
8520 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
8521 and translated to @w{@code{@var{a} = @var{a op b}}}.
8522 @w{@code{@var{op}=}} and @code{=} have the same precedence.
8523 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
8524 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
8527 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
8528 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
8532 Logical @sc{or}. Defined on integral types.
8535 Logical @sc{and}. Defined on integral types.
8538 Bitwise @sc{or}. Defined on integral types.
8541 Bitwise exclusive-@sc{or}. Defined on integral types.
8544 Bitwise @sc{and}. Defined on integral types.
8547 Equality and inequality. Defined on scalar types. The value of these
8548 expressions is 0 for false and non-zero for true.
8550 @item <@r{, }>@r{, }<=@r{, }>=
8551 Less than, greater than, less than or equal, greater than or equal.
8552 Defined on scalar types. The value of these expressions is 0 for false
8553 and non-zero for true.
8556 left shift, and right shift. Defined on integral types.
8559 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8562 Addition and subtraction. Defined on integral types, floating-point types and
8565 @item *@r{, }/@r{, }%
8566 Multiplication, division, and modulus. Multiplication and division are
8567 defined on integral and floating-point types. Modulus is defined on
8571 Increment and decrement. When appearing before a variable, the
8572 operation is performed before the variable is used in an expression;
8573 when appearing after it, the variable's value is used before the
8574 operation takes place.
8577 Pointer dereferencing. Defined on pointer types. Same precedence as
8581 Address operator. Defined on variables. Same precedence as @code{++}.
8583 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
8584 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
8585 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
8586 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
8590 Negative. Defined on integral and floating-point types. Same
8591 precedence as @code{++}.
8594 Logical negation. Defined on integral types. Same precedence as
8598 Bitwise complement operator. Defined on integral types. Same precedence as
8603 Structure member, and pointer-to-structure member. For convenience,
8604 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
8605 pointer based on the stored type information.
8606 Defined on @code{struct} and @code{union} data.
8609 Dereferences of pointers to members.
8612 Array indexing. @code{@var{a}[@var{i}]} is defined as
8613 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
8616 Function parameter list. Same precedence as @code{->}.
8619 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
8620 and @code{class} types.
8623 Doubled colons also represent the @value{GDBN} scope operator
8624 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
8628 If an operator is redefined in the user code, @value{GDBN} usually
8629 attempts to invoke the redefined version instead of using the operator's
8637 @subsubsection C and C@t{++} constants
8639 @cindex C and C@t{++} constants
8641 @value{GDBN} allows you to express the constants of C and C@t{++} in the
8646 Integer constants are a sequence of digits. Octal constants are
8647 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
8648 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
8649 @samp{l}, specifying that the constant should be treated as a
8653 Floating point constants are a sequence of digits, followed by a decimal
8654 point, followed by a sequence of digits, and optionally followed by an
8655 exponent. An exponent is of the form:
8656 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
8657 sequence of digits. The @samp{+} is optional for positive exponents.
8658 A floating-point constant may also end with a letter @samp{f} or
8659 @samp{F}, specifying that the constant should be treated as being of
8660 the @code{float} (as opposed to the default @code{double}) type; or with
8661 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
8665 Enumerated constants consist of enumerated identifiers, or their
8666 integral equivalents.
8669 Character constants are a single character surrounded by single quotes
8670 (@code{'}), or a number---the ordinal value of the corresponding character
8671 (usually its @sc{ascii} value). Within quotes, the single character may
8672 be represented by a letter or by @dfn{escape sequences}, which are of
8673 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
8674 of the character's ordinal value; or of the form @samp{\@var{x}}, where
8675 @samp{@var{x}} is a predefined special character---for example,
8676 @samp{\n} for newline.
8679 String constants are a sequence of character constants surrounded by
8680 double quotes (@code{"}). Any valid character constant (as described
8681 above) may appear. Double quotes within the string must be preceded by
8682 a backslash, so for instance @samp{"a\"b'c"} is a string of five
8686 Pointer constants are an integral value. You can also write pointers
8687 to constants using the C operator @samp{&}.
8690 Array constants are comma-separated lists surrounded by braces @samp{@{}
8691 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
8692 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
8693 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
8697 * C plus plus expressions::
8704 @node C plus plus expressions
8705 @subsubsection C@t{++} expressions
8707 @cindex expressions in C@t{++}
8708 @value{GDBN} expression handling can interpret most C@t{++} expressions.
8710 @cindex debugging C@t{++} programs
8711 @cindex C@t{++} compilers
8712 @cindex debug formats and C@t{++}
8713 @cindex @value{NGCC} and C@t{++}
8715 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
8716 proper compiler and the proper debug format. Currently, @value{GDBN}
8717 works best when debugging C@t{++} code that is compiled with
8718 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
8719 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
8720 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
8721 stabs+ as their default debug format, so you usually don't need to
8722 specify a debug format explicitly. Other compilers and/or debug formats
8723 are likely to work badly or not at all when using @value{GDBN} to debug
8729 @cindex member functions
8731 Member function calls are allowed; you can use expressions like
8734 count = aml->GetOriginal(x, y)
8737 @vindex this@r{, inside C@t{++} member functions}
8738 @cindex namespace in C@t{++}
8740 While a member function is active (in the selected stack frame), your
8741 expressions have the same namespace available as the member function;
8742 that is, @value{GDBN} allows implicit references to the class instance
8743 pointer @code{this} following the same rules as C@t{++}.
8745 @cindex call overloaded functions
8746 @cindex overloaded functions, calling
8747 @cindex type conversions in C@t{++}
8749 You can call overloaded functions; @value{GDBN} resolves the function
8750 call to the right definition, with some restrictions. @value{GDBN} does not
8751 perform overload resolution involving user-defined type conversions,
8752 calls to constructors, or instantiations of templates that do not exist
8753 in the program. It also cannot handle ellipsis argument lists or
8756 It does perform integral conversions and promotions, floating-point
8757 promotions, arithmetic conversions, pointer conversions, conversions of
8758 class objects to base classes, and standard conversions such as those of
8759 functions or arrays to pointers; it requires an exact match on the
8760 number of function arguments.
8762 Overload resolution is always performed, unless you have specified
8763 @code{set overload-resolution off}. @xref{Debugging C plus plus,
8764 ,@value{GDBN} features for C@t{++}}.
8766 You must specify @code{set overload-resolution off} in order to use an
8767 explicit function signature to call an overloaded function, as in
8769 p 'foo(char,int)'('x', 13)
8772 The @value{GDBN} command-completion facility can simplify this;
8773 see @ref{Completion, ,Command completion}.
8775 @cindex reference declarations
8777 @value{GDBN} understands variables declared as C@t{++} references; you can use
8778 them in expressions just as you do in C@t{++} source---they are automatically
8781 In the parameter list shown when @value{GDBN} displays a frame, the values of
8782 reference variables are not displayed (unlike other variables); this
8783 avoids clutter, since references are often used for large structures.
8784 The @emph{address} of a reference variable is always shown, unless
8785 you have specified @samp{set print address off}.
8788 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
8789 expressions can use it just as expressions in your program do. Since
8790 one scope may be defined in another, you can use @code{::} repeatedly if
8791 necessary, for example in an expression like
8792 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
8793 resolving name scope by reference to source files, in both C and C@t{++}
8794 debugging (@pxref{Variables, ,Program variables}).
8797 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
8798 calling virtual functions correctly, printing out virtual bases of
8799 objects, calling functions in a base subobject, casting objects, and
8800 invoking user-defined operators.
8803 @subsubsection C and C@t{++} defaults
8805 @cindex C and C@t{++} defaults
8807 If you allow @value{GDBN} to set type and range checking automatically, they
8808 both default to @code{off} whenever the working language changes to
8809 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
8810 selects the working language.
8812 If you allow @value{GDBN} to set the language automatically, it
8813 recognizes source files whose names end with @file{.c}, @file{.C}, or
8814 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
8815 these files, it sets the working language to C or C@t{++}.
8816 @xref{Automatically, ,Having @value{GDBN} infer the source language},
8817 for further details.
8819 @c Type checking is (a) primarily motivated by Modula-2, and (b)
8820 @c unimplemented. If (b) changes, it might make sense to let this node
8821 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
8824 @subsubsection C and C@t{++} type and range checks
8826 @cindex C and C@t{++} checks
8828 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
8829 is not used. However, if you turn type checking on, @value{GDBN}
8830 considers two variables type equivalent if:
8834 The two variables are structured and have the same structure, union, or
8838 The two variables have the same type name, or types that have been
8839 declared equivalent through @code{typedef}.
8842 @c leaving this out because neither J Gilmore nor R Pesch understand it.
8845 The two @code{struct}, @code{union}, or @code{enum} variables are
8846 declared in the same declaration. (Note: this may not be true for all C
8851 Range checking, if turned on, is done on mathematical operations. Array
8852 indices are not checked, since they are often used to index a pointer
8853 that is not itself an array.
8856 @subsubsection @value{GDBN} and C
8858 The @code{set print union} and @code{show print union} commands apply to
8859 the @code{union} type. When set to @samp{on}, any @code{union} that is
8860 inside a @code{struct} or @code{class} is also printed. Otherwise, it
8861 appears as @samp{@{...@}}.
8863 The @code{@@} operator aids in the debugging of dynamic arrays, formed
8864 with pointers and a memory allocation function. @xref{Expressions,
8868 * Debugging C plus plus::
8871 @node Debugging C plus plus
8872 @subsubsection @value{GDBN} features for C@t{++}
8874 @cindex commands for C@t{++}
8876 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
8877 designed specifically for use with C@t{++}. Here is a summary:
8880 @cindex break in overloaded functions
8881 @item @r{breakpoint menus}
8882 When you want a breakpoint in a function whose name is overloaded,
8883 @value{GDBN} breakpoint menus help you specify which function definition
8884 you want. @xref{Breakpoint Menus,,Breakpoint menus}.
8886 @cindex overloading in C@t{++}
8887 @item rbreak @var{regex}
8888 Setting breakpoints using regular expressions is helpful for setting
8889 breakpoints on overloaded functions that are not members of any special
8891 @xref{Set Breaks, ,Setting breakpoints}.
8893 @cindex C@t{++} exception handling
8896 Debug C@t{++} exception handling using these commands. @xref{Set
8897 Catchpoints, , Setting catchpoints}.
8900 @item ptype @var{typename}
8901 Print inheritance relationships as well as other information for type
8903 @xref{Symbols, ,Examining the Symbol Table}.
8905 @cindex C@t{++} symbol display
8906 @item set print demangle
8907 @itemx show print demangle
8908 @itemx set print asm-demangle
8909 @itemx show print asm-demangle
8910 Control whether C@t{++} symbols display in their source form, both when
8911 displaying code as C@t{++} source and when displaying disassemblies.
8912 @xref{Print Settings, ,Print settings}.
8914 @item set print object
8915 @itemx show print object
8916 Choose whether to print derived (actual) or declared types of objects.
8917 @xref{Print Settings, ,Print settings}.
8919 @item set print vtbl
8920 @itemx show print vtbl
8921 Control the format for printing virtual function tables.
8922 @xref{Print Settings, ,Print settings}.
8923 (The @code{vtbl} commands do not work on programs compiled with the HP
8924 ANSI C@t{++} compiler (@code{aCC}).)
8926 @kindex set overload-resolution
8927 @cindex overloaded functions, overload resolution
8928 @item set overload-resolution on
8929 Enable overload resolution for C@t{++} expression evaluation. The default
8930 is on. For overloaded functions, @value{GDBN} evaluates the arguments
8931 and searches for a function whose signature matches the argument types,
8932 using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++}
8933 expressions}, for details). If it cannot find a match, it emits a
8936 @item set overload-resolution off
8937 Disable overload resolution for C@t{++} expression evaluation. For
8938 overloaded functions that are not class member functions, @value{GDBN}
8939 chooses the first function of the specified name that it finds in the
8940 symbol table, whether or not its arguments are of the correct type. For
8941 overloaded functions that are class member functions, @value{GDBN}
8942 searches for a function whose signature @emph{exactly} matches the
8945 @kindex show overload-resolution
8946 @item show overload-resolution
8947 Show the current setting of overload resolution.
8949 @item @r{Overloaded symbol names}
8950 You can specify a particular definition of an overloaded symbol, using
8951 the same notation that is used to declare such symbols in C@t{++}: type
8952 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
8953 also use the @value{GDBN} command-line word completion facilities to list the
8954 available choices, or to finish the type list for you.
8955 @xref{Completion,, Command completion}, for details on how to do this.
8959 @subsection Objective-C
8962 This section provides information about some commands and command
8963 options that are useful for debugging Objective-C code. See also
8964 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
8965 few more commands specific to Objective-C support.
8968 * Method Names in Commands::
8969 * The Print Command with Objective-C::
8972 @node Method Names in Commands, The Print Command with Objective-C, Objective-C, Objective-C
8973 @subsubsection Method Names in Commands
8975 The following commands have been extended to accept Objective-C method
8976 names as line specifications:
8978 @kindex clear@r{, and Objective-C}
8979 @kindex break@r{, and Objective-C}
8980 @kindex info line@r{, and Objective-C}
8981 @kindex jump@r{, and Objective-C}
8982 @kindex list@r{, and Objective-C}
8986 @item @code{info line}
8991 A fully qualified Objective-C method name is specified as
8994 -[@var{Class} @var{methodName}]
8997 where the minus sign is used to indicate an instance method and a
8998 plus sign (not shown) is used to indicate a class method. The class
8999 name @var{Class} and method name @var{methodName} are enclosed in
9000 brackets, similar to the way messages are specified in Objective-C
9001 source code. For example, to set a breakpoint at the @code{create}
9002 instance method of class @code{Fruit} in the program currently being
9006 break -[Fruit create]
9009 To list ten program lines around the @code{initialize} class method,
9013 list +[NSText initialize]
9016 In the current version of @value{GDBN}, the plus or minus sign is
9017 required. In future versions of @value{GDBN}, the plus or minus
9018 sign will be optional, but you can use it to narrow the search. It
9019 is also possible to specify just a method name:
9025 You must specify the complete method name, including any colons. If
9026 your program's source files contain more than one @code{create} method,
9027 you'll be presented with a numbered list of classes that implement that
9028 method. Indicate your choice by number, or type @samp{0} to exit if
9031 As another example, to clear a breakpoint established at the
9032 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
9035 clear -[NSWindow makeKeyAndOrderFront:]
9038 @node The Print Command with Objective-C
9039 @subsubsection The Print Command With Objective-C
9040 @cindex Objective-C, print objects
9041 @kindex print-object
9042 @kindex po @r{(@code{print-object})}
9044 The print command has also been extended to accept methods. For example:
9047 print -[@var{object} hash]
9050 @cindex print an Objective-C object description
9051 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
9053 will tell @value{GDBN} to send the @code{hash} message to @var{object}
9054 and print the result. Also, an additional command has been added,
9055 @code{print-object} or @code{po} for short, which is meant to print
9056 the description of an object. However, this command may only work
9057 with certain Objective-C libraries that have a particular hook
9058 function, @code{_NSPrintForDebugger}, defined.
9062 @cindex Fortran-specific support in @value{GDBN}
9065 @cindex @code{COMMON} blocks, Fortran
9067 @item info common @r{[}@var{common-name}@r{]}
9068 This command prints the values contained in the Fortran @code{COMMON}
9069 block whose name is @var{common-name}. With no argument, the names of
9070 all @code{COMMON} blocks visible at current program location are
9074 Fortran symbols are usually case-insensitive, so @value{GDBN} by
9075 default uses case-insensitive matches for Fortran symbols. You can
9076 change that with the @samp{set case-insensitive} command, see
9077 @ref{Symbols}, for the details.
9082 @cindex Pascal support in @value{GDBN}, limitations
9083 Debugging Pascal programs which use sets, subranges, file variables, or
9084 nested functions does not currently work. @value{GDBN} does not support
9085 entering expressions, printing values, or similar features using Pascal
9088 The Pascal-specific command @code{set print pascal_static-members}
9089 controls whether static members of Pascal objects are displayed.
9090 @xref{Print Settings, pascal_static-members}.
9093 @subsection Modula-2
9095 @cindex Modula-2, @value{GDBN} support
9097 The extensions made to @value{GDBN} to support Modula-2 only support
9098 output from the @sc{gnu} Modula-2 compiler (which is currently being
9099 developed). Other Modula-2 compilers are not currently supported, and
9100 attempting to debug executables produced by them is most likely
9101 to give an error as @value{GDBN} reads in the executable's symbol
9104 @cindex expressions in Modula-2
9106 * M2 Operators:: Built-in operators
9107 * Built-In Func/Proc:: Built-in functions and procedures
9108 * M2 Constants:: Modula-2 constants
9109 * M2 Defaults:: Default settings for Modula-2
9110 * Deviations:: Deviations from standard Modula-2
9111 * M2 Checks:: Modula-2 type and range checks
9112 * M2 Scope:: The scope operators @code{::} and @code{.}
9113 * GDB/M2:: @value{GDBN} and Modula-2
9117 @subsubsection Operators
9118 @cindex Modula-2 operators
9120 Operators must be defined on values of specific types. For instance,
9121 @code{+} is defined on numbers, but not on structures. Operators are
9122 often defined on groups of types. For the purposes of Modula-2, the
9123 following definitions hold:
9128 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
9132 @emph{Character types} consist of @code{CHAR} and its subranges.
9135 @emph{Floating-point types} consist of @code{REAL}.
9138 @emph{Pointer types} consist of anything declared as @code{POINTER TO
9142 @emph{Scalar types} consist of all of the above.
9145 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
9148 @emph{Boolean types} consist of @code{BOOLEAN}.
9152 The following operators are supported, and appear in order of
9153 increasing precedence:
9157 Function argument or array index separator.
9160 Assignment. The value of @var{var} @code{:=} @var{value} is
9164 Less than, greater than on integral, floating-point, or enumerated
9168 Less than or equal to, greater than or equal to
9169 on integral, floating-point and enumerated types, or set inclusion on
9170 set types. Same precedence as @code{<}.
9172 @item =@r{, }<>@r{, }#
9173 Equality and two ways of expressing inequality, valid on scalar types.
9174 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
9175 available for inequality, since @code{#} conflicts with the script
9179 Set membership. Defined on set types and the types of their members.
9180 Same precedence as @code{<}.
9183 Boolean disjunction. Defined on boolean types.
9186 Boolean conjunction. Defined on boolean types.
9189 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9192 Addition and subtraction on integral and floating-point types, or union
9193 and difference on set types.
9196 Multiplication on integral and floating-point types, or set intersection
9200 Division on floating-point types, or symmetric set difference on set
9201 types. Same precedence as @code{*}.
9204 Integer division and remainder. Defined on integral types. Same
9205 precedence as @code{*}.
9208 Negative. Defined on @code{INTEGER} and @code{REAL} data.
9211 Pointer dereferencing. Defined on pointer types.
9214 Boolean negation. Defined on boolean types. Same precedence as
9218 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
9219 precedence as @code{^}.
9222 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
9225 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
9229 @value{GDBN} and Modula-2 scope operators.
9233 @emph{Warning:} Sets and their operations are not yet supported, so @value{GDBN}
9234 treats the use of the operator @code{IN}, or the use of operators
9235 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
9236 @code{<=}, and @code{>=} on sets as an error.
9240 @node Built-In Func/Proc
9241 @subsubsection Built-in functions and procedures
9242 @cindex Modula-2 built-ins
9244 Modula-2 also makes available several built-in procedures and functions.
9245 In describing these, the following metavariables are used:
9250 represents an @code{ARRAY} variable.
9253 represents a @code{CHAR} constant or variable.
9256 represents a variable or constant of integral type.
9259 represents an identifier that belongs to a set. Generally used in the
9260 same function with the metavariable @var{s}. The type of @var{s} should
9261 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
9264 represents a variable or constant of integral or floating-point type.
9267 represents a variable or constant of floating-point type.
9273 represents a variable.
9276 represents a variable or constant of one of many types. See the
9277 explanation of the function for details.
9280 All Modula-2 built-in procedures also return a result, described below.
9284 Returns the absolute value of @var{n}.
9287 If @var{c} is a lower case letter, it returns its upper case
9288 equivalent, otherwise it returns its argument.
9291 Returns the character whose ordinal value is @var{i}.
9294 Decrements the value in the variable @var{v} by one. Returns the new value.
9296 @item DEC(@var{v},@var{i})
9297 Decrements the value in the variable @var{v} by @var{i}. Returns the
9300 @item EXCL(@var{m},@var{s})
9301 Removes the element @var{m} from the set @var{s}. Returns the new
9304 @item FLOAT(@var{i})
9305 Returns the floating point equivalent of the integer @var{i}.
9308 Returns the index of the last member of @var{a}.
9311 Increments the value in the variable @var{v} by one. Returns the new value.
9313 @item INC(@var{v},@var{i})
9314 Increments the value in the variable @var{v} by @var{i}. Returns the
9317 @item INCL(@var{m},@var{s})
9318 Adds the element @var{m} to the set @var{s} if it is not already
9319 there. Returns the new set.
9322 Returns the maximum value of the type @var{t}.
9325 Returns the minimum value of the type @var{t}.
9328 Returns boolean TRUE if @var{i} is an odd number.
9331 Returns the ordinal value of its argument. For example, the ordinal
9332 value of a character is its @sc{ascii} value (on machines supporting the
9333 @sc{ascii} character set). @var{x} must be of an ordered type, which include
9334 integral, character and enumerated types.
9337 Returns the size of its argument. @var{x} can be a variable or a type.
9339 @item TRUNC(@var{r})
9340 Returns the integral part of @var{r}.
9342 @item VAL(@var{t},@var{i})
9343 Returns the member of the type @var{t} whose ordinal value is @var{i}.
9347 @emph{Warning:} Sets and their operations are not yet supported, so
9348 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
9352 @cindex Modula-2 constants
9354 @subsubsection Constants
9356 @value{GDBN} allows you to express the constants of Modula-2 in the following
9362 Integer constants are simply a sequence of digits. When used in an
9363 expression, a constant is interpreted to be type-compatible with the
9364 rest of the expression. Hexadecimal integers are specified by a
9365 trailing @samp{H}, and octal integers by a trailing @samp{B}.
9368 Floating point constants appear as a sequence of digits, followed by a
9369 decimal point and another sequence of digits. An optional exponent can
9370 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
9371 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
9372 digits of the floating point constant must be valid decimal (base 10)
9376 Character constants consist of a single character enclosed by a pair of
9377 like quotes, either single (@code{'}) or double (@code{"}). They may
9378 also be expressed by their ordinal value (their @sc{ascii} value, usually)
9379 followed by a @samp{C}.
9382 String constants consist of a sequence of characters enclosed by a
9383 pair of like quotes, either single (@code{'}) or double (@code{"}).
9384 Escape sequences in the style of C are also allowed. @xref{C
9385 Constants, ,C and C@t{++} constants}, for a brief explanation of escape
9389 Enumerated constants consist of an enumerated identifier.
9392 Boolean constants consist of the identifiers @code{TRUE} and
9396 Pointer constants consist of integral values only.
9399 Set constants are not yet supported.
9403 @subsubsection Modula-2 defaults
9404 @cindex Modula-2 defaults
9406 If type and range checking are set automatically by @value{GDBN}, they
9407 both default to @code{on} whenever the working language changes to
9408 Modula-2. This happens regardless of whether you or @value{GDBN}
9409 selected the working language.
9411 If you allow @value{GDBN} to set the language automatically, then entering
9412 code compiled from a file whose name ends with @file{.mod} sets the
9413 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set
9414 the language automatically}, for further details.
9417 @subsubsection Deviations from standard Modula-2
9418 @cindex Modula-2, deviations from
9420 A few changes have been made to make Modula-2 programs easier to debug.
9421 This is done primarily via loosening its type strictness:
9425 Unlike in standard Modula-2, pointer constants can be formed by
9426 integers. This allows you to modify pointer variables during
9427 debugging. (In standard Modula-2, the actual address contained in a
9428 pointer variable is hidden from you; it can only be modified
9429 through direct assignment to another pointer variable or expression that
9430 returned a pointer.)
9433 C escape sequences can be used in strings and characters to represent
9434 non-printable characters. @value{GDBN} prints out strings with these
9435 escape sequences embedded. Single non-printable characters are
9436 printed using the @samp{CHR(@var{nnn})} format.
9439 The assignment operator (@code{:=}) returns the value of its right-hand
9443 All built-in procedures both modify @emph{and} return their argument.
9447 @subsubsection Modula-2 type and range checks
9448 @cindex Modula-2 checks
9451 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
9454 @c FIXME remove warning when type/range checks added
9456 @value{GDBN} considers two Modula-2 variables type equivalent if:
9460 They are of types that have been declared equivalent via a @code{TYPE
9461 @var{t1} = @var{t2}} statement
9464 They have been declared on the same line. (Note: This is true of the
9465 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
9468 As long as type checking is enabled, any attempt to combine variables
9469 whose types are not equivalent is an error.
9471 Range checking is done on all mathematical operations, assignment, array
9472 index bounds, and all built-in functions and procedures.
9475 @subsubsection The scope operators @code{::} and @code{.}
9477 @cindex @code{.}, Modula-2 scope operator
9478 @cindex colon, doubled as scope operator
9480 @vindex colon-colon@r{, in Modula-2}
9481 @c Info cannot handle :: but TeX can.
9484 @vindex ::@r{, in Modula-2}
9487 There are a few subtle differences between the Modula-2 scope operator
9488 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
9493 @var{module} . @var{id}
9494 @var{scope} :: @var{id}
9498 where @var{scope} is the name of a module or a procedure,
9499 @var{module} the name of a module, and @var{id} is any declared
9500 identifier within your program, except another module.
9502 Using the @code{::} operator makes @value{GDBN} search the scope
9503 specified by @var{scope} for the identifier @var{id}. If it is not
9504 found in the specified scope, then @value{GDBN} searches all scopes
9505 enclosing the one specified by @var{scope}.
9507 Using the @code{.} operator makes @value{GDBN} search the current scope for
9508 the identifier specified by @var{id} that was imported from the
9509 definition module specified by @var{module}. With this operator, it is
9510 an error if the identifier @var{id} was not imported from definition
9511 module @var{module}, or if @var{id} is not an identifier in
9515 @subsubsection @value{GDBN} and Modula-2
9517 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
9518 Five subcommands of @code{set print} and @code{show print} apply
9519 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
9520 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
9521 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
9522 analogue in Modula-2.
9524 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
9525 with any language, is not useful with Modula-2. Its
9526 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
9527 created in Modula-2 as they can in C or C@t{++}. However, because an
9528 address can be specified by an integral constant, the construct
9529 @samp{@{@var{type}@}@var{adrexp}} is still useful.
9531 @cindex @code{#} in Modula-2
9532 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
9533 interpreted as the beginning of a comment. Use @code{<>} instead.
9539 The extensions made to @value{GDBN} for Ada only support
9540 output from the @sc{gnu} Ada (GNAT) compiler.
9541 Other Ada compilers are not currently supported, and
9542 attempting to debug executables produced by them is most likely
9546 @cindex expressions in Ada
9548 * Ada Mode Intro:: General remarks on the Ada syntax
9549 and semantics supported by Ada mode
9551 * Omissions from Ada:: Restrictions on the Ada expression syntax.
9552 * Additions to Ada:: Extensions of the Ada expression syntax.
9553 * Stopping Before Main Program:: Debugging the program during elaboration.
9554 * Ada Glitches:: Known peculiarities of Ada mode.
9557 @node Ada Mode Intro
9558 @subsubsection Introduction
9559 @cindex Ada mode, general
9561 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
9562 syntax, with some extensions.
9563 The philosophy behind the design of this subset is
9567 That @value{GDBN} should provide basic literals and access to operations for
9568 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
9569 leaving more sophisticated computations to subprograms written into the
9570 program (which therefore may be called from @value{GDBN}).
9573 That type safety and strict adherence to Ada language restrictions
9574 are not particularly important to the @value{GDBN} user.
9577 That brevity is important to the @value{GDBN} user.
9580 Thus, for brevity, the debugger acts as if there were
9581 implicit @code{with} and @code{use} clauses in effect for all user-written
9582 packages, making it unnecessary to fully qualify most names with
9583 their packages, regardless of context. Where this causes ambiguity,
9584 @value{GDBN} asks the user's intent.
9586 The debugger will start in Ada mode if it detects an Ada main program.
9587 As for other languages, it will enter Ada mode when stopped in a program that
9588 was translated from an Ada source file.
9590 While in Ada mode, you may use `@t{--}' for comments. This is useful
9591 mostly for documenting command files. The standard @value{GDBN} comment
9592 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
9593 middle (to allow based literals).
9595 The debugger supports limited overloading. Given a subprogram call in which
9596 the function symbol has multiple definitions, it will use the number of
9597 actual parameters and some information about their types to attempt to narrow
9598 the set of definitions. It also makes very limited use of context, preferring
9599 procedures to functions in the context of the @code{call} command, and
9600 functions to procedures elsewhere.
9602 @node Omissions from Ada
9603 @subsubsection Omissions from Ada
9604 @cindex Ada, omissions from
9606 Here are the notable omissions from the subset:
9610 Only a subset of the attributes are supported:
9614 @t{'First}, @t{'Last}, and @t{'Length}
9615 on array objects (not on types and subtypes).
9618 @t{'Min} and @t{'Max}.
9621 @t{'Pos} and @t{'Val}.
9627 @t{'Range} on array objects (not subtypes), but only as the right
9628 operand of the membership (@code{in}) operator.
9631 @t{'Access}, @t{'Unchecked_Access}, and
9632 @t{'Unrestricted_Access} (a GNAT extension).
9640 @code{Characters.Latin_1} are not available and
9641 concatenation is not implemented. Thus, escape characters in strings are
9642 not currently available.
9645 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
9646 equality of representations. They will generally work correctly
9647 for strings and arrays whose elements have integer or enumeration types.
9648 They may not work correctly for arrays whose element
9649 types have user-defined equality, for arrays of real values
9650 (in particular, IEEE-conformant floating point, because of negative
9651 zeroes and NaNs), and for arrays whose elements contain unused bits with
9652 indeterminate values.
9655 The other component-by-component array operations (@code{and}, @code{or},
9656 @code{xor}, @code{not}, and relational tests other than equality)
9657 are not implemented.
9660 There are no record or array aggregates.
9663 Calls to dispatching subprograms are not implemented.
9666 The overloading algorithm is much more limited (i.e., less selective)
9667 than that of real Ada. It makes only limited use of the context in which a subexpression
9668 appears to resolve its meaning, and it is much looser in its rules for allowing
9669 type matches. As a result, some function calls will be ambiguous, and the user
9670 will be asked to choose the proper resolution.
9673 The @code{new} operator is not implemented.
9676 Entry calls are not implemented.
9679 Aside from printing, arithmetic operations on the native VAX floating-point
9680 formats are not supported.
9683 It is not possible to slice a packed array.
9686 @node Additions to Ada
9687 @subsubsection Additions to Ada
9688 @cindex Ada, deviations from
9690 As it does for other languages, @value{GDBN} makes certain generic
9691 extensions to Ada (@pxref{Expressions}):
9695 If the expression @var{E} is a variable residing in memory
9696 (typically a local variable or array element) and @var{N} is
9697 a positive integer, then @code{@var{E}@@@var{N}} displays the values of
9698 @var{E} and the @var{N}-1 adjacent variables following it in memory as an array.
9699 In Ada, this operator is generally not necessary, since its prime use
9700 is in displaying parts of an array, and slicing will usually do this in Ada.
9701 However, there are occasional uses when debugging programs
9702 in which certain debugging information has been optimized away.
9705 @code{@var{B}::@var{var}} means ``the variable named @var{var} that appears
9706 in function or file @var{B}.'' When @var{B} is a file name, you must typically
9707 surround it in single quotes.
9710 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
9711 @var{type} that appears at address @var{addr}.''
9714 A name starting with @samp{$} is a convenience variable
9715 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
9718 In addition, @value{GDBN} provides a few other shortcuts and outright additions specific
9723 The assignment statement is allowed as an expression, returning
9724 its right-hand operand as its value. Thus, you may enter
9728 print A(tmp := y + 1)
9732 The semicolon is allowed as an ``operator,'' returning as its value
9733 the value of its right-hand operand.
9734 This allows, for example,
9735 complex conditional breaks:
9739 condition 1 (report(i); k += 1; A(k) > 100)
9743 Rather than use catenation and symbolic character names to introduce special
9744 characters into strings, one may instead use a special bracket notation,
9745 which is also used to print strings. A sequence of characters of the form
9746 @samp{["@var{XX}"]} within a string or character literal denotes the
9747 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
9748 sequence of characters @samp{["""]} also denotes a single quotation mark
9749 in strings. For example,
9751 "One line.["0a"]Next line.["0a"]"
9754 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF}) after each
9758 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
9759 @t{'Max} is optional (and is ignored in any case). For example, it is valid
9767 When printing arrays, @value{GDBN} uses positional notation when the
9768 array has a lower bound of 1, and uses a modified named notation otherwise.
9769 For example, a one-dimensional array of three integers with a lower bound of 3 might print as
9776 That is, in contrast to valid Ada, only the first component has a @code{=>}
9780 You may abbreviate attributes in expressions with any unique,
9781 multi-character subsequence of
9782 their names (an exact match gets preference).
9783 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
9784 in place of @t{a'length}.
9787 @cindex quoting Ada internal identifiers
9788 Since Ada is case-insensitive, the debugger normally maps identifiers you type
9789 to lower case. The GNAT compiler uses upper-case characters for
9790 some of its internal identifiers, which are normally of no interest to users.
9791 For the rare occasions when you actually have to look at them,
9792 enclose them in angle brackets to avoid the lower-case mapping.
9795 @value{GDBP} print <JMPBUF_SAVE>[0]
9799 Printing an object of class-wide type or dereferencing an
9800 access-to-class-wide value will display all the components of the object's
9801 specific type (as indicated by its run-time tag). Likewise, component
9802 selection on such a value will operate on the specific type of the
9807 @node Stopping Before Main Program
9808 @subsubsection Stopping at the Very Beginning
9810 @cindex breakpointing Ada elaboration code
9811 It is sometimes necessary to debug the program during elaboration, and
9812 before reaching the main procedure.
9813 As defined in the Ada Reference
9814 Manual, the elaboration code is invoked from a procedure called
9815 @code{adainit}. To run your program up to the beginning of
9816 elaboration, simply use the following two commands:
9817 @code{tbreak adainit} and @code{run}.
9820 @subsubsection Known Peculiarities of Ada Mode
9821 @cindex Ada, problems
9823 Besides the omissions listed previously (@pxref{Omissions from Ada}),
9824 we know of several problems with and limitations of Ada mode in
9826 some of which will be fixed with planned future releases of the debugger
9827 and the GNU Ada compiler.
9831 Currently, the debugger
9832 has insufficient information to determine whether certain pointers represent
9833 pointers to objects or the objects themselves.
9834 Thus, the user may have to tack an extra @code{.all} after an expression
9835 to get it printed properly.
9838 Static constants that the compiler chooses not to materialize as objects in
9839 storage are invisible to the debugger.
9842 Named parameter associations in function argument lists are ignored (the
9843 argument lists are treated as positional).
9846 Many useful library packages are currently invisible to the debugger.
9849 Fixed-point arithmetic, conversions, input, and output is carried out using
9850 floating-point arithmetic, and may give results that only approximate those on
9854 The type of the @t{'Address} attribute may not be @code{System.Address}.
9857 The GNAT compiler never generates the prefix @code{Standard} for any of
9858 the standard symbols defined by the Ada language. @value{GDBN} knows about
9859 this: it will strip the prefix from names when you use it, and will never
9860 look for a name you have so qualified among local symbols, nor match against
9861 symbols in other packages or subprograms. If you have
9862 defined entities anywhere in your program other than parameters and
9863 local variables whose simple names match names in @code{Standard},
9864 GNAT's lack of qualification here can cause confusion. When this happens,
9865 you can usually resolve the confusion
9866 by qualifying the problematic names with package
9867 @code{Standard} explicitly.
9870 @node Unsupported languages
9871 @section Unsupported languages
9873 @cindex unsupported languages
9874 @cindex minimal language
9875 In addition to the other fully-supported programming languages,
9876 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
9877 It does not represent a real programming language, but provides a set
9878 of capabilities close to what the C or assembly languages provide.
9879 This should allow most simple operations to be performed while debugging
9880 an application that uses a language currently not supported by @value{GDBN}.
9882 If the language is set to @code{auto}, @value{GDBN} will automatically
9883 select this language if the current frame corresponds to an unsupported
9887 @chapter Examining the Symbol Table
9889 The commands described in this chapter allow you to inquire about the
9890 symbols (names of variables, functions and types) defined in your
9891 program. This information is inherent in the text of your program and
9892 does not change as your program executes. @value{GDBN} finds it in your
9893 program's symbol table, in the file indicated when you started @value{GDBN}
9894 (@pxref{File Options, ,Choosing files}), or by one of the
9895 file-management commands (@pxref{Files, ,Commands to specify files}).
9897 @cindex symbol names
9898 @cindex names of symbols
9899 @cindex quoting names
9900 Occasionally, you may need to refer to symbols that contain unusual
9901 characters, which @value{GDBN} ordinarily treats as word delimiters. The
9902 most frequent case is in referring to static variables in other
9903 source files (@pxref{Variables,,Program variables}). File names
9904 are recorded in object files as debugging symbols, but @value{GDBN} would
9905 ordinarily parse a typical file name, like @file{foo.c}, as the three words
9906 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
9907 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
9914 looks up the value of @code{x} in the scope of the file @file{foo.c}.
9917 @cindex case-insensitive symbol names
9918 @cindex case sensitivity in symbol names
9919 @kindex set case-sensitive
9920 @item set case-sensitive on
9921 @itemx set case-sensitive off
9922 @itemx set case-sensitive auto
9923 Normally, when @value{GDBN} looks up symbols, it matches their names
9924 with case sensitivity determined by the current source language.
9925 Occasionally, you may wish to control that. The command @code{set
9926 case-sensitive} lets you do that by specifying @code{on} for
9927 case-sensitive matches or @code{off} for case-insensitive ones. If
9928 you specify @code{auto}, case sensitivity is reset to the default
9929 suitable for the source language. The default is case-sensitive
9930 matches for all languages except for Fortran, for which the default is
9931 case-insensitive matches.
9933 @kindex show case-sensitive
9934 @item show case-sensitive
9935 This command shows the current setting of case sensitivity for symbols
9938 @kindex info address
9939 @cindex address of a symbol
9940 @item info address @var{symbol}
9941 Describe where the data for @var{symbol} is stored. For a register
9942 variable, this says which register it is kept in. For a non-register
9943 local variable, this prints the stack-frame offset at which the variable
9946 Note the contrast with @samp{print &@var{symbol}}, which does not work
9947 at all for a register variable, and for a stack local variable prints
9948 the exact address of the current instantiation of the variable.
9951 @cindex symbol from address
9952 @cindex closest symbol and offset for an address
9953 @item info symbol @var{addr}
9954 Print the name of a symbol which is stored at the address @var{addr}.
9955 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
9956 nearest symbol and an offset from it:
9959 (@value{GDBP}) info symbol 0x54320
9960 _initialize_vx + 396 in section .text
9964 This is the opposite of the @code{info address} command. You can use
9965 it to find out the name of a variable or a function given its address.
9968 @item whatis @var{expr}
9969 Print the data type of expression @var{expr}. @var{expr} is not
9970 actually evaluated, and any side-effecting operations (such as
9971 assignments or function calls) inside it do not take place.
9972 @xref{Expressions, ,Expressions}.
9975 Print the data type of @code{$}, the last value in the value history.
9978 @item ptype @var{typename}
9979 Print a description of data type @var{typename}. @var{typename} may be
9980 the name of a type, or for C code it may have the form @samp{class
9981 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
9982 @var{union-tag}} or @samp{enum @var{enum-tag}}.
9984 @item ptype @var{expr}
9986 Print a description of the type of expression @var{expr}. @code{ptype}
9987 differs from @code{whatis} by printing a detailed description, instead
9988 of just the name of the type.
9990 For example, for this variable declaration:
9993 struct complex @{double real; double imag;@} v;
9997 the two commands give this output:
10001 (@value{GDBP}) whatis v
10002 type = struct complex
10003 (@value{GDBP}) ptype v
10004 type = struct complex @{
10012 As with @code{whatis}, using @code{ptype} without an argument refers to
10013 the type of @code{$}, the last value in the value history.
10016 @item info types @var{regexp}
10018 Print a brief description of all types whose names match the regular
10019 expression @var{regexp} (or all types in your program, if you supply
10020 no argument). Each complete typename is matched as though it were a
10021 complete line; thus, @samp{i type value} gives information on all
10022 types in your program whose names include the string @code{value}, but
10023 @samp{i type ^value$} gives information only on types whose complete
10024 name is @code{value}.
10026 This command differs from @code{ptype} in two ways: first, like
10027 @code{whatis}, it does not print a detailed description; second, it
10028 lists all source files where a type is defined.
10031 @cindex local variables
10032 @item info scope @var{location}
10033 List all the variables local to a particular scope. This command
10034 accepts a @var{location} argument---a function name, a source line, or
10035 an address preceded by a @samp{*}, and prints all the variables local
10036 to the scope defined by that location. For example:
10039 (@value{GDBP}) @b{info scope command_line_handler}
10040 Scope for command_line_handler:
10041 Symbol rl is an argument at stack/frame offset 8, length 4.
10042 Symbol linebuffer is in static storage at address 0x150a18, length 4.
10043 Symbol linelength is in static storage at address 0x150a1c, length 4.
10044 Symbol p is a local variable in register $esi, length 4.
10045 Symbol p1 is a local variable in register $ebx, length 4.
10046 Symbol nline is a local variable in register $edx, length 4.
10047 Symbol repeat is a local variable at frame offset -8, length 4.
10051 This command is especially useful for determining what data to collect
10052 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
10055 @kindex info source
10057 Show information about the current source file---that is, the source file for
10058 the function containing the current point of execution:
10061 the name of the source file, and the directory containing it,
10063 the directory it was compiled in,
10065 its length, in lines,
10067 which programming language it is written in,
10069 whether the executable includes debugging information for that file, and
10070 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
10072 whether the debugging information includes information about
10073 preprocessor macros.
10077 @kindex info sources
10079 Print the names of all source files in your program for which there is
10080 debugging information, organized into two lists: files whose symbols
10081 have already been read, and files whose symbols will be read when needed.
10083 @kindex info functions
10084 @item info functions
10085 Print the names and data types of all defined functions.
10087 @item info functions @var{regexp}
10088 Print the names and data types of all defined functions
10089 whose names contain a match for regular expression @var{regexp}.
10090 Thus, @samp{info fun step} finds all functions whose names
10091 include @code{step}; @samp{info fun ^step} finds those whose names
10092 start with @code{step}. If a function name contains characters
10093 that conflict with the regular expression language (eg.
10094 @samp{operator*()}), they may be quoted with a backslash.
10096 @kindex info variables
10097 @item info variables
10098 Print the names and data types of all variables that are declared
10099 outside of functions (i.e.@: excluding local variables).
10101 @item info variables @var{regexp}
10102 Print the names and data types of all variables (except for local
10103 variables) whose names contain a match for regular expression
10106 @kindex info classes
10107 @cindex Objective-C, classes and selectors
10109 @itemx info classes @var{regexp}
10110 Display all Objective-C classes in your program, or
10111 (with the @var{regexp} argument) all those matching a particular regular
10114 @kindex info selectors
10115 @item info selectors
10116 @itemx info selectors @var{regexp}
10117 Display all Objective-C selectors in your program, or
10118 (with the @var{regexp} argument) all those matching a particular regular
10122 This was never implemented.
10123 @kindex info methods
10125 @itemx info methods @var{regexp}
10126 The @code{info methods} command permits the user to examine all defined
10127 methods within C@t{++} program, or (with the @var{regexp} argument) a
10128 specific set of methods found in the various C@t{++} classes. Many
10129 C@t{++} classes provide a large number of methods. Thus, the output
10130 from the @code{ptype} command can be overwhelming and hard to use. The
10131 @code{info-methods} command filters the methods, printing only those
10132 which match the regular-expression @var{regexp}.
10135 @cindex reloading symbols
10136 Some systems allow individual object files that make up your program to
10137 be replaced without stopping and restarting your program. For example,
10138 in VxWorks you can simply recompile a defective object file and keep on
10139 running. If you are running on one of these systems, you can allow
10140 @value{GDBN} to reload the symbols for automatically relinked modules:
10143 @kindex set symbol-reloading
10144 @item set symbol-reloading on
10145 Replace symbol definitions for the corresponding source file when an
10146 object file with a particular name is seen again.
10148 @item set symbol-reloading off
10149 Do not replace symbol definitions when encountering object files of the
10150 same name more than once. This is the default state; if you are not
10151 running on a system that permits automatic relinking of modules, you
10152 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
10153 may discard symbols when linking large programs, that may contain
10154 several modules (from different directories or libraries) with the same
10157 @kindex show symbol-reloading
10158 @item show symbol-reloading
10159 Show the current @code{on} or @code{off} setting.
10162 @cindex opaque data types
10163 @kindex set opaque-type-resolution
10164 @item set opaque-type-resolution on
10165 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
10166 declared as a pointer to a @code{struct}, @code{class}, or
10167 @code{union}---for example, @code{struct MyType *}---that is used in one
10168 source file although the full declaration of @code{struct MyType} is in
10169 another source file. The default is on.
10171 A change in the setting of this subcommand will not take effect until
10172 the next time symbols for a file are loaded.
10174 @item set opaque-type-resolution off
10175 Tell @value{GDBN} not to resolve opaque types. In this case, the type
10176 is printed as follows:
10178 @{<no data fields>@}
10181 @kindex show opaque-type-resolution
10182 @item show opaque-type-resolution
10183 Show whether opaque types are resolved or not.
10185 @kindex maint print symbols
10186 @cindex symbol dump
10187 @kindex maint print psymbols
10188 @cindex partial symbol dump
10189 @item maint print symbols @var{filename}
10190 @itemx maint print psymbols @var{filename}
10191 @itemx maint print msymbols @var{filename}
10192 Write a dump of debugging symbol data into the file @var{filename}.
10193 These commands are used to debug the @value{GDBN} symbol-reading code. Only
10194 symbols with debugging data are included. If you use @samp{maint print
10195 symbols}, @value{GDBN} includes all the symbols for which it has already
10196 collected full details: that is, @var{filename} reflects symbols for
10197 only those files whose symbols @value{GDBN} has read. You can use the
10198 command @code{info sources} to find out which files these are. If you
10199 use @samp{maint print psymbols} instead, the dump shows information about
10200 symbols that @value{GDBN} only knows partially---that is, symbols defined in
10201 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
10202 @samp{maint print msymbols} dumps just the minimal symbol information
10203 required for each object file from which @value{GDBN} has read some symbols.
10204 @xref{Files, ,Commands to specify files}, for a discussion of how
10205 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
10207 @kindex maint info symtabs
10208 @kindex maint info psymtabs
10209 @cindex listing @value{GDBN}'s internal symbol tables
10210 @cindex symbol tables, listing @value{GDBN}'s internal
10211 @cindex full symbol tables, listing @value{GDBN}'s internal
10212 @cindex partial symbol tables, listing @value{GDBN}'s internal
10213 @item maint info symtabs @r{[} @var{regexp} @r{]}
10214 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
10216 List the @code{struct symtab} or @code{struct partial_symtab}
10217 structures whose names match @var{regexp}. If @var{regexp} is not
10218 given, list them all. The output includes expressions which you can
10219 copy into a @value{GDBN} debugging this one to examine a particular
10220 structure in more detail. For example:
10223 (@value{GDBP}) maint info psymtabs dwarf2read
10224 @{ objfile /home/gnu/build/gdb/gdb
10225 ((struct objfile *) 0x82e69d0)
10226 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
10227 ((struct partial_symtab *) 0x8474b10)
10230 text addresses 0x814d3c8 -- 0x8158074
10231 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
10232 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
10233 dependencies (none)
10236 (@value{GDBP}) maint info symtabs
10240 We see that there is one partial symbol table whose filename contains
10241 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
10242 and we see that @value{GDBN} has not read in any symtabs yet at all.
10243 If we set a breakpoint on a function, that will cause @value{GDBN} to
10244 read the symtab for the compilation unit containing that function:
10247 (@value{GDBP}) break dwarf2_psymtab_to_symtab
10248 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
10250 (@value{GDBP}) maint info symtabs
10251 @{ objfile /home/gnu/build/gdb/gdb
10252 ((struct objfile *) 0x82e69d0)
10253 @{ symtab /home/gnu/src/gdb/dwarf2read.c
10254 ((struct symtab *) 0x86c1f38)
10257 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
10258 debugformat DWARF 2
10267 @chapter Altering Execution
10269 Once you think you have found an error in your program, you might want to
10270 find out for certain whether correcting the apparent error would lead to
10271 correct results in the rest of the run. You can find the answer by
10272 experiment, using the @value{GDBN} features for altering execution of the
10275 For example, you can store new values into variables or memory
10276 locations, give your program a signal, restart it at a different
10277 address, or even return prematurely from a function.
10280 * Assignment:: Assignment to variables
10281 * Jumping:: Continuing at a different address
10282 * Signaling:: Giving your program a signal
10283 * Returning:: Returning from a function
10284 * Calling:: Calling your program's functions
10285 * Patching:: Patching your program
10289 @section Assignment to variables
10292 @cindex setting variables
10293 To alter the value of a variable, evaluate an assignment expression.
10294 @xref{Expressions, ,Expressions}. For example,
10301 stores the value 4 into the variable @code{x}, and then prints the
10302 value of the assignment expression (which is 4).
10303 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
10304 information on operators in supported languages.
10306 @kindex set variable
10307 @cindex variables, setting
10308 If you are not interested in seeing the value of the assignment, use the
10309 @code{set} command instead of the @code{print} command. @code{set} is
10310 really the same as @code{print} except that the expression's value is
10311 not printed and is not put in the value history (@pxref{Value History,
10312 ,Value history}). The expression is evaluated only for its effects.
10314 If the beginning of the argument string of the @code{set} command
10315 appears identical to a @code{set} subcommand, use the @code{set
10316 variable} command instead of just @code{set}. This command is identical
10317 to @code{set} except for its lack of subcommands. For example, if your
10318 program has a variable @code{width}, you get an error if you try to set
10319 a new value with just @samp{set width=13}, because @value{GDBN} has the
10320 command @code{set width}:
10323 (@value{GDBP}) whatis width
10325 (@value{GDBP}) p width
10327 (@value{GDBP}) set width=47
10328 Invalid syntax in expression.
10332 The invalid expression, of course, is @samp{=47}. In
10333 order to actually set the program's variable @code{width}, use
10336 (@value{GDBP}) set var width=47
10339 Because the @code{set} command has many subcommands that can conflict
10340 with the names of program variables, it is a good idea to use the
10341 @code{set variable} command instead of just @code{set}. For example, if
10342 your program has a variable @code{g}, you run into problems if you try
10343 to set a new value with just @samp{set g=4}, because @value{GDBN} has
10344 the command @code{set gnutarget}, abbreviated @code{set g}:
10348 (@value{GDBP}) whatis g
10352 (@value{GDBP}) set g=4
10356 The program being debugged has been started already.
10357 Start it from the beginning? (y or n) y
10358 Starting program: /home/smith/cc_progs/a.out
10359 "/home/smith/cc_progs/a.out": can't open to read symbols:
10360 Invalid bfd target.
10361 (@value{GDBP}) show g
10362 The current BFD target is "=4".
10367 The program variable @code{g} did not change, and you silently set the
10368 @code{gnutarget} to an invalid value. In order to set the variable
10372 (@value{GDBP}) set var g=4
10375 @value{GDBN} allows more implicit conversions in assignments than C; you can
10376 freely store an integer value into a pointer variable or vice versa,
10377 and you can convert any structure to any other structure that is the
10378 same length or shorter.
10379 @comment FIXME: how do structs align/pad in these conversions?
10380 @comment /doc@cygnus.com 18dec1990
10382 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
10383 construct to generate a value of specified type at a specified address
10384 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
10385 to memory location @code{0x83040} as an integer (which implies a certain size
10386 and representation in memory), and
10389 set @{int@}0x83040 = 4
10393 stores the value 4 into that memory location.
10396 @section Continuing at a different address
10398 Ordinarily, when you continue your program, you do so at the place where
10399 it stopped, with the @code{continue} command. You can instead continue at
10400 an address of your own choosing, with the following commands:
10404 @item jump @var{linespec}
10405 Resume execution at line @var{linespec}. Execution stops again
10406 immediately if there is a breakpoint there. @xref{List, ,Printing
10407 source lines}, for a description of the different forms of
10408 @var{linespec}. It is common practice to use the @code{tbreak} command
10409 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
10412 The @code{jump} command does not change the current stack frame, or
10413 the stack pointer, or the contents of any memory location or any
10414 register other than the program counter. If line @var{linespec} is in
10415 a different function from the one currently executing, the results may
10416 be bizarre if the two functions expect different patterns of arguments or
10417 of local variables. For this reason, the @code{jump} command requests
10418 confirmation if the specified line is not in the function currently
10419 executing. However, even bizarre results are predictable if you are
10420 well acquainted with the machine-language code of your program.
10422 @item jump *@var{address}
10423 Resume execution at the instruction at address @var{address}.
10426 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
10427 On many systems, you can get much the same effect as the @code{jump}
10428 command by storing a new value into the register @code{$pc}. The
10429 difference is that this does not start your program running; it only
10430 changes the address of where it @emph{will} run when you continue. For
10438 makes the next @code{continue} command or stepping command execute at
10439 address @code{0x485}, rather than at the address where your program stopped.
10440 @xref{Continuing and Stepping, ,Continuing and stepping}.
10442 The most common occasion to use the @code{jump} command is to back
10443 up---perhaps with more breakpoints set---over a portion of a program
10444 that has already executed, in order to examine its execution in more
10449 @section Giving your program a signal
10450 @cindex deliver a signal to a program
10454 @item signal @var{signal}
10455 Resume execution where your program stopped, but immediately give it the
10456 signal @var{signal}. @var{signal} can be the name or the number of a
10457 signal. For example, on many systems @code{signal 2} and @code{signal
10458 SIGINT} are both ways of sending an interrupt signal.
10460 Alternatively, if @var{signal} is zero, continue execution without
10461 giving a signal. This is useful when your program stopped on account of
10462 a signal and would ordinary see the signal when resumed with the
10463 @code{continue} command; @samp{signal 0} causes it to resume without a
10466 @code{signal} does not repeat when you press @key{RET} a second time
10467 after executing the command.
10471 Invoking the @code{signal} command is not the same as invoking the
10472 @code{kill} utility from the shell. Sending a signal with @code{kill}
10473 causes @value{GDBN} to decide what to do with the signal depending on
10474 the signal handling tables (@pxref{Signals}). The @code{signal} command
10475 passes the signal directly to your program.
10479 @section Returning from a function
10482 @cindex returning from a function
10485 @itemx return @var{expression}
10486 You can cancel execution of a function call with the @code{return}
10487 command. If you give an
10488 @var{expression} argument, its value is used as the function's return
10492 When you use @code{return}, @value{GDBN} discards the selected stack frame
10493 (and all frames within it). You can think of this as making the
10494 discarded frame return prematurely. If you wish to specify a value to
10495 be returned, give that value as the argument to @code{return}.
10497 This pops the selected stack frame (@pxref{Selection, ,Selecting a
10498 frame}), and any other frames inside of it, leaving its caller as the
10499 innermost remaining frame. That frame becomes selected. The
10500 specified value is stored in the registers used for returning values
10503 The @code{return} command does not resume execution; it leaves the
10504 program stopped in the state that would exist if the function had just
10505 returned. In contrast, the @code{finish} command (@pxref{Continuing
10506 and Stepping, ,Continuing and stepping}) resumes execution until the
10507 selected stack frame returns naturally.
10510 @section Calling program functions
10513 @cindex calling functions
10514 @cindex inferior functions, calling
10515 @item print @var{expr}
10516 Evaluate the expression @var{expr} and display the resuling value.
10517 @var{expr} may include calls to functions in the program being
10521 @item call @var{expr}
10522 Evaluate the expression @var{expr} without displaying @code{void}
10525 You can use this variant of the @code{print} command if you want to
10526 execute a function from your program that does not return anything
10527 (a.k.a.@: @dfn{a void function}), but without cluttering the output
10528 with @code{void} returned values that @value{GDBN} will otherwise
10529 print. If the result is not void, it is printed and saved in the
10533 It is possible for the function you call via the @code{print} or
10534 @code{call} command to generate a signal (e.g., if there's a bug in
10535 the function, or if you passed it incorrect arguments). What happens
10536 in that case is controlled by the @code{set unwindonsignal} command.
10539 @item set unwindonsignal
10540 @kindex set unwindonsignal
10541 @cindex unwind stack in called functions
10542 @cindex call dummy stack unwinding
10543 Set unwinding of the stack if a signal is received while in a function
10544 that @value{GDBN} called in the program being debugged. If set to on,
10545 @value{GDBN} unwinds the stack it created for the call and restores
10546 the context to what it was before the call. If set to off (the
10547 default), @value{GDBN} stops in the frame where the signal was
10550 @item show unwindonsignal
10551 @kindex show unwindonsignal
10552 Show the current setting of stack unwinding in the functions called by
10556 @cindex weak alias functions
10557 Sometimes, a function you wish to call is actually a @dfn{weak alias}
10558 for another function. In such case, @value{GDBN} might not pick up
10559 the type information, including the types of the function arguments,
10560 which causes @value{GDBN} to call the inferior function incorrectly.
10561 As a result, the called function will function erroneously and may
10562 even crash. A solution to that is to use the name of the aliased
10566 @section Patching programs
10568 @cindex patching binaries
10569 @cindex writing into executables
10570 @cindex writing into corefiles
10572 By default, @value{GDBN} opens the file containing your program's
10573 executable code (or the corefile) read-only. This prevents accidental
10574 alterations to machine code; but it also prevents you from intentionally
10575 patching your program's binary.
10577 If you'd like to be able to patch the binary, you can specify that
10578 explicitly with the @code{set write} command. For example, you might
10579 want to turn on internal debugging flags, or even to make emergency
10585 @itemx set write off
10586 If you specify @samp{set write on}, @value{GDBN} opens executable and
10587 core files for both reading and writing; if you specify @samp{set write
10588 off} (the default), @value{GDBN} opens them read-only.
10590 If you have already loaded a file, you must load it again (using the
10591 @code{exec-file} or @code{core-file} command) after changing @code{set
10592 write}, for your new setting to take effect.
10596 Display whether executable files and core files are opened for writing
10597 as well as reading.
10601 @chapter @value{GDBN} Files
10603 @value{GDBN} needs to know the file name of the program to be debugged,
10604 both in order to read its symbol table and in order to start your
10605 program. To debug a core dump of a previous run, you must also tell
10606 @value{GDBN} the name of the core dump file.
10609 * Files:: Commands to specify files
10610 * Separate Debug Files:: Debugging information in separate files
10611 * Symbol Errors:: Errors reading symbol files
10615 @section Commands to specify files
10617 @cindex symbol table
10618 @cindex core dump file
10620 You may want to specify executable and core dump file names. The usual
10621 way to do this is at start-up time, using the arguments to
10622 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
10623 Out of @value{GDBN}}).
10625 Occasionally it is necessary to change to a different file during a
10626 @value{GDBN} session. Or you may run @value{GDBN} and forget to
10627 specify a file you want to use. Or you are debugging a remote target
10628 via @code{gdbserver} (@pxref{Server, file}). In these situations the
10629 @value{GDBN} commands to specify new files are useful.
10632 @cindex executable file
10634 @item file @var{filename}
10635 Use @var{filename} as the program to be debugged. It is read for its
10636 symbols and for the contents of pure memory. It is also the program
10637 executed when you use the @code{run} command. If you do not specify a
10638 directory and the file is not found in the @value{GDBN} working directory,
10639 @value{GDBN} uses the environment variable @code{PATH} as a list of
10640 directories to search, just as the shell does when looking for a program
10641 to run. You can change the value of this variable, for both @value{GDBN}
10642 and your program, using the @code{path} command.
10644 On systems with memory-mapped files, an auxiliary file named
10645 @file{@var{filename}.syms} may hold symbol table information for
10646 @var{filename}. If so, @value{GDBN} maps in the symbol table from
10647 @file{@var{filename}.syms}, starting up more quickly. See the
10648 descriptions of the file options @samp{-mapped} and @samp{-readnow}
10649 (available on the command line, see @ref{File Options, , -readnow},
10650 and with the commands @code{file}, @code{symbol-file}, or
10651 @code{add-symbol-file}, described below), for more information.
10654 @code{file} with no argument makes @value{GDBN} discard any information it
10655 has on both executable file and the symbol table.
10658 @item exec-file @r{[} @var{filename} @r{]}
10659 Specify that the program to be run (but not the symbol table) is found
10660 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
10661 if necessary to locate your program. Omitting @var{filename} means to
10662 discard information on the executable file.
10664 @kindex symbol-file
10665 @item symbol-file @r{[} @var{filename} @r{]}
10666 Read symbol table information from file @var{filename}. @code{PATH} is
10667 searched when necessary. Use the @code{file} command to get both symbol
10668 table and program to run from the same file.
10670 @code{symbol-file} with no argument clears out @value{GDBN} information on your
10671 program's symbol table.
10673 The @code{symbol-file} command causes @value{GDBN} to forget the contents
10674 of its convenience variables, the value history, and all breakpoints and
10675 auto-display expressions. This is because they may contain pointers to
10676 the internal data recording symbols and data types, which are part of
10677 the old symbol table data being discarded inside @value{GDBN}.
10679 @code{symbol-file} does not repeat if you press @key{RET} again after
10682 When @value{GDBN} is configured for a particular environment, it
10683 understands debugging information in whatever format is the standard
10684 generated for that environment; you may use either a @sc{gnu} compiler, or
10685 other compilers that adhere to the local conventions.
10686 Best results are usually obtained from @sc{gnu} compilers; for example,
10687 using @code{@value{GCC}} you can generate debugging information for
10690 For most kinds of object files, with the exception of old SVR3 systems
10691 using COFF, the @code{symbol-file} command does not normally read the
10692 symbol table in full right away. Instead, it scans the symbol table
10693 quickly to find which source files and which symbols are present. The
10694 details are read later, one source file at a time, as they are needed.
10696 The purpose of this two-stage reading strategy is to make @value{GDBN}
10697 start up faster. For the most part, it is invisible except for
10698 occasional pauses while the symbol table details for a particular source
10699 file are being read. (The @code{set verbose} command can turn these
10700 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
10701 warnings and messages}.)
10703 We have not implemented the two-stage strategy for COFF yet. When the
10704 symbol table is stored in COFF format, @code{symbol-file} reads the
10705 symbol table data in full right away. Note that ``stabs-in-COFF''
10706 still does the two-stage strategy, since the debug info is actually
10710 @cindex reading symbols immediately
10711 @cindex symbols, reading immediately
10713 @cindex memory-mapped symbol file
10714 @cindex saving symbol table
10715 @item symbol-file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10716 @itemx file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10717 You can override the @value{GDBN} two-stage strategy for reading symbol
10718 tables by using the @samp{-readnow} option with any of the commands that
10719 load symbol table information, if you want to be sure @value{GDBN} has the
10720 entire symbol table available.
10722 If memory-mapped files are available on your system through the
10723 @code{mmap} system call, you can use another option, @samp{-mapped}, to
10724 cause @value{GDBN} to write the symbols for your program into a reusable
10725 file. Future @value{GDBN} debugging sessions map in symbol information
10726 from this auxiliary symbol file (if the program has not changed), rather
10727 than spending time reading the symbol table from the executable
10728 program. Using the @samp{-mapped} option has the same effect as
10729 starting @value{GDBN} with the @samp{-mapped} command-line option.
10731 You can use both options together, to make sure the auxiliary symbol
10732 file has all the symbol information for your program.
10734 The auxiliary symbol file for a program called @var{myprog} is called
10735 @samp{@var{myprog}.syms}. Once this file exists (so long as it is newer
10736 than the corresponding executable), @value{GDBN} always attempts to use
10737 it when you debug @var{myprog}; no special options or commands are
10740 The @file{.syms} file is specific to the host machine where you run
10741 @value{GDBN}. It holds an exact image of the internal @value{GDBN}
10742 symbol table. It cannot be shared across multiple host platforms.
10744 @c FIXME: for now no mention of directories, since this seems to be in
10745 @c flux. 13mar1992 status is that in theory GDB would look either in
10746 @c current dir or in same dir as myprog; but issues like competing
10747 @c GDB's, or clutter in system dirs, mean that in practice right now
10748 @c only current dir is used. FFish says maybe a special GDB hierarchy
10749 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
10753 @item core-file @r{[}@var{filename}@r{]}
10755 Specify the whereabouts of a core dump file to be used as the ``contents
10756 of memory''. Traditionally, core files contain only some parts of the
10757 address space of the process that generated them; @value{GDBN} can access the
10758 executable file itself for other parts.
10760 @code{core-file} with no argument specifies that no core file is
10763 Note that the core file is ignored when your program is actually running
10764 under @value{GDBN}. So, if you have been running your program and you
10765 wish to debug a core file instead, you must kill the subprocess in which
10766 the program is running. To do this, use the @code{kill} command
10767 (@pxref{Kill Process, ,Killing the child process}).
10769 @kindex add-symbol-file
10770 @cindex dynamic linking
10771 @item add-symbol-file @var{filename} @var{address}
10772 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10773 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
10774 The @code{add-symbol-file} command reads additional symbol table
10775 information from the file @var{filename}. You would use this command
10776 when @var{filename} has been dynamically loaded (by some other means)
10777 into the program that is running. @var{address} should be the memory
10778 address at which the file has been loaded; @value{GDBN} cannot figure
10779 this out for itself. You can additionally specify an arbitrary number
10780 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
10781 section name and base address for that section. You can specify any
10782 @var{address} as an expression.
10784 The symbol table of the file @var{filename} is added to the symbol table
10785 originally read with the @code{symbol-file} command. You can use the
10786 @code{add-symbol-file} command any number of times; the new symbol data
10787 thus read keeps adding to the old. To discard all old symbol data
10788 instead, use the @code{symbol-file} command without any arguments.
10790 @cindex relocatable object files, reading symbols from
10791 @cindex object files, relocatable, reading symbols from
10792 @cindex reading symbols from relocatable object files
10793 @cindex symbols, reading from relocatable object files
10794 @cindex @file{.o} files, reading symbols from
10795 Although @var{filename} is typically a shared library file, an
10796 executable file, or some other object file which has been fully
10797 relocated for loading into a process, you can also load symbolic
10798 information from relocatable @file{.o} files, as long as:
10802 the file's symbolic information refers only to linker symbols defined in
10803 that file, not to symbols defined by other object files,
10805 every section the file's symbolic information refers to has actually
10806 been loaded into the inferior, as it appears in the file, and
10808 you can determine the address at which every section was loaded, and
10809 provide these to the @code{add-symbol-file} command.
10813 Some embedded operating systems, like Sun Chorus and VxWorks, can load
10814 relocatable files into an already running program; such systems
10815 typically make the requirements above easy to meet. However, it's
10816 important to recognize that many native systems use complex link
10817 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
10818 assembly, for example) that make the requirements difficult to meet. In
10819 general, one cannot assume that using @code{add-symbol-file} to read a
10820 relocatable object file's symbolic information will have the same effect
10821 as linking the relocatable object file into the program in the normal
10824 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
10826 You can use the @samp{-mapped} and @samp{-readnow} options just as with
10827 the @code{symbol-file} command, to change how @value{GDBN} manages the symbol
10828 table information for @var{filename}.
10830 @kindex add-symbol-file-from-memory
10831 @cindex @code{syscall DSO}
10832 @cindex load symbols from memory
10833 @item add-symbol-file-from-memory @var{address}
10834 Load symbols from the given @var{address} in a dynamically loaded
10835 object file whose image is mapped directly into the inferior's memory.
10836 For example, the Linux kernel maps a @code{syscall DSO} into each
10837 process's address space; this DSO provides kernel-specific code for
10838 some system calls. The argument can be any expression whose
10839 evaluation yields the address of the file's shared object file header.
10840 For this command to work, you must have used @code{symbol-file} or
10841 @code{exec-file} commands in advance.
10843 @kindex add-shared-symbol-files
10845 @item add-shared-symbol-files @var{library-file}
10846 @itemx assf @var{library-file}
10847 The @code{add-shared-symbol-files} command can currently be used only
10848 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
10849 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
10850 @value{GDBN} automatically looks for shared libraries, however if
10851 @value{GDBN} does not find yours, you can invoke
10852 @code{add-shared-symbol-files}. It takes one argument: the shared
10853 library's file name. @code{assf} is a shorthand alias for
10854 @code{add-shared-symbol-files}.
10857 @item section @var{section} @var{addr}
10858 The @code{section} command changes the base address of the named
10859 @var{section} of the exec file to @var{addr}. This can be used if the
10860 exec file does not contain section addresses, (such as in the
10861 @code{a.out} format), or when the addresses specified in the file
10862 itself are wrong. Each section must be changed separately. The
10863 @code{info files} command, described below, lists all the sections and
10867 @kindex info target
10870 @code{info files} and @code{info target} are synonymous; both print the
10871 current target (@pxref{Targets, ,Specifying a Debugging Target}),
10872 including the names of the executable and core dump files currently in
10873 use by @value{GDBN}, and the files from which symbols were loaded. The
10874 command @code{help target} lists all possible targets rather than
10877 @kindex maint info sections
10878 @item maint info sections
10879 Another command that can give you extra information about program sections
10880 is @code{maint info sections}. In addition to the section information
10881 displayed by @code{info files}, this command displays the flags and file
10882 offset of each section in the executable and core dump files. In addition,
10883 @code{maint info sections} provides the following command options (which
10884 may be arbitrarily combined):
10888 Display sections for all loaded object files, including shared libraries.
10889 @item @var{sections}
10890 Display info only for named @var{sections}.
10891 @item @var{section-flags}
10892 Display info only for sections for which @var{section-flags} are true.
10893 The section flags that @value{GDBN} currently knows about are:
10896 Section will have space allocated in the process when loaded.
10897 Set for all sections except those containing debug information.
10899 Section will be loaded from the file into the child process memory.
10900 Set for pre-initialized code and data, clear for @code{.bss} sections.
10902 Section needs to be relocated before loading.
10904 Section cannot be modified by the child process.
10906 Section contains executable code only.
10908 Section contains data only (no executable code).
10910 Section will reside in ROM.
10912 Section contains data for constructor/destructor lists.
10914 Section is not empty.
10916 An instruction to the linker to not output the section.
10917 @item COFF_SHARED_LIBRARY
10918 A notification to the linker that the section contains
10919 COFF shared library information.
10921 Section contains common symbols.
10924 @kindex set trust-readonly-sections
10925 @cindex read-only sections
10926 @item set trust-readonly-sections on
10927 Tell @value{GDBN} that readonly sections in your object file
10928 really are read-only (i.e.@: that their contents will not change).
10929 In that case, @value{GDBN} can fetch values from these sections
10930 out of the object file, rather than from the target program.
10931 For some targets (notably embedded ones), this can be a significant
10932 enhancement to debugging performance.
10934 The default is off.
10936 @item set trust-readonly-sections off
10937 Tell @value{GDBN} not to trust readonly sections. This means that
10938 the contents of the section might change while the program is running,
10939 and must therefore be fetched from the target when needed.
10941 @item show trust-readonly-sections
10942 Show the current setting of trusting readonly sections.
10945 All file-specifying commands allow both absolute and relative file names
10946 as arguments. @value{GDBN} always converts the file name to an absolute file
10947 name and remembers it that way.
10949 @cindex shared libraries
10950 @value{GDBN} supports GNU/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
10951 and IBM RS/6000 AIX shared libraries.
10953 @value{GDBN} automatically loads symbol definitions from shared libraries
10954 when you use the @code{run} command, or when you examine a core file.
10955 (Before you issue the @code{run} command, @value{GDBN} does not understand
10956 references to a function in a shared library, however---unless you are
10957 debugging a core file).
10959 On HP-UX, if the program loads a library explicitly, @value{GDBN}
10960 automatically loads the symbols at the time of the @code{shl_load} call.
10962 @c FIXME: some @value{GDBN} release may permit some refs to undef
10963 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
10964 @c FIXME...lib; check this from time to time when updating manual
10966 There are times, however, when you may wish to not automatically load
10967 symbol definitions from shared libraries, such as when they are
10968 particularly large or there are many of them.
10970 To control the automatic loading of shared library symbols, use the
10974 @kindex set auto-solib-add
10975 @item set auto-solib-add @var{mode}
10976 If @var{mode} is @code{on}, symbols from all shared object libraries
10977 will be loaded automatically when the inferior begins execution, you
10978 attach to an independently started inferior, or when the dynamic linker
10979 informs @value{GDBN} that a new library has been loaded. If @var{mode}
10980 is @code{off}, symbols must be loaded manually, using the
10981 @code{sharedlibrary} command. The default value is @code{on}.
10983 @cindex memory used for symbol tables
10984 If your program uses lots of shared libraries with debug info that
10985 takes large amounts of memory, you can decrease the @value{GDBN}
10986 memory footprint by preventing it from automatically loading the
10987 symbols from shared libraries. To that end, type @kbd{set
10988 auto-solib-add off} before running the inferior, then load each
10989 library whose debug symbols you do need with @kbd{sharedlibrary
10990 @var{regexp}}, where @var{regexp} is a regular expresion that matches
10991 the libraries whose symbols you want to be loaded.
10993 @kindex show auto-solib-add
10994 @item show auto-solib-add
10995 Display the current autoloading mode.
10998 @cindex load shared library
10999 To explicitly load shared library symbols, use the @code{sharedlibrary}
11003 @kindex info sharedlibrary
11006 @itemx info sharedlibrary
11007 Print the names of the shared libraries which are currently loaded.
11009 @kindex sharedlibrary
11011 @item sharedlibrary @var{regex}
11012 @itemx share @var{regex}
11013 Load shared object library symbols for files matching a
11014 Unix regular expression.
11015 As with files loaded automatically, it only loads shared libraries
11016 required by your program for a core file or after typing @code{run}. If
11017 @var{regex} is omitted all shared libraries required by your program are
11020 @item nosharedlibrary
11021 @kindex nosharedlibrary
11022 @cindex unload symbols from shared libraries
11023 Unload all shared object library symbols. This discards all symbols
11024 that have been loaded from all shared libraries. Symbols from shared
11025 libraries that were loaded by explicit user requests are not
11029 Sometimes you may wish that @value{GDBN} stops and gives you control
11030 when any of shared library events happen. Use the @code{set
11031 stop-on-solib-events} command for this:
11034 @item set stop-on-solib-events
11035 @kindex set stop-on-solib-events
11036 This command controls whether @value{GDBN} should give you control
11037 when the dynamic linker notifies it about some shared library event.
11038 The most common event of interest is loading or unloading of a new
11041 @item show stop-on-solib-events
11042 @kindex show stop-on-solib-events
11043 Show whether @value{GDBN} stops and gives you control when shared
11044 library events happen.
11047 Shared libraries are also supported in many cross or remote debugging
11048 configurations. A copy of the target's libraries need to be present on the
11049 host system; they need to be the same as the target libraries, although the
11050 copies on the target can be stripped as long as the copies on the host are
11053 You need to tell @value{GDBN} where the target libraries are, so that it can
11054 load the correct copies---otherwise, it may try to load the host's libraries.
11055 @value{GDBN} has two variables to specify the search directories for target
11059 @kindex set solib-absolute-prefix
11060 @item set solib-absolute-prefix @var{path}
11061 If this variable is set, @var{path} will be used as a prefix for any
11062 absolute shared library paths; many runtime loaders store the absolute
11063 paths to the shared library in the target program's memory. If you use
11064 @samp{solib-absolute-prefix} to find shared libraries, they need to be laid
11065 out in the same way that they are on the target, with e.g.@: a
11066 @file{/usr/lib} hierarchy under @var{path}.
11068 You can set the default value of @samp{solib-absolute-prefix} by using the
11069 configure-time @samp{--with-sysroot} option.
11071 @kindex show solib-absolute-prefix
11072 @item show solib-absolute-prefix
11073 Display the current shared library prefix.
11075 @kindex set solib-search-path
11076 @item set solib-search-path @var{path}
11077 If this variable is set, @var{path} is a colon-separated list of directories
11078 to search for shared libraries. @samp{solib-search-path} is used after
11079 @samp{solib-absolute-prefix} fails to locate the library, or if the path to
11080 the library is relative instead of absolute. If you want to use
11081 @samp{solib-search-path} instead of @samp{solib-absolute-prefix}, be sure to
11082 set @samp{solib-absolute-prefix} to a nonexistant directory to prevent
11083 @value{GDBN} from finding your host's libraries.
11085 @kindex show solib-search-path
11086 @item show solib-search-path
11087 Display the current shared library search path.
11091 @node Separate Debug Files
11092 @section Debugging Information in Separate Files
11093 @cindex separate debugging information files
11094 @cindex debugging information in separate files
11095 @cindex @file{.debug} subdirectories
11096 @cindex debugging information directory, global
11097 @cindex global debugging information directory
11099 @value{GDBN} allows you to put a program's debugging information in a
11100 file separate from the executable itself, in a way that allows
11101 @value{GDBN} to find and load the debugging information automatically.
11102 Since debugging information can be very large --- sometimes larger
11103 than the executable code itself --- some systems distribute debugging
11104 information for their executables in separate files, which users can
11105 install only when they need to debug a problem.
11107 If an executable's debugging information has been extracted to a
11108 separate file, the executable should contain a @dfn{debug link} giving
11109 the name of the debugging information file (with no directory
11110 components), and a checksum of its contents. (The exact form of a
11111 debug link is described below.) If the full name of the directory
11112 containing the executable is @var{execdir}, and the executable has a
11113 debug link that specifies the name @var{debugfile}, then @value{GDBN}
11114 will automatically search for the debugging information file in three
11119 the directory containing the executable file (that is, it will look
11120 for a file named @file{@var{execdir}/@var{debugfile}},
11122 a subdirectory of that directory named @file{.debug} (that is, the
11123 file @file{@var{execdir}/.debug/@var{debugfile}}, and
11125 a subdirectory of the global debug file directory that includes the
11126 executable's full path, and the name from the link (that is, the file
11127 @file{@var{globaldebugdir}/@var{execdir}/@var{debugfile}}, where
11128 @var{globaldebugdir} is the global debug file directory, and
11129 @var{execdir} has been turned into a relative path).
11132 @value{GDBN} checks under each of these names for a debugging
11133 information file whose checksum matches that given in the link, and
11134 reads the debugging information from the first one it finds.
11136 So, for example, if you ask @value{GDBN} to debug @file{/usr/bin/ls},
11137 which has a link containing the name @file{ls.debug}, and the global
11138 debug directory is @file{/usr/lib/debug}, then @value{GDBN} will look
11139 for debug information in @file{/usr/bin/ls.debug},
11140 @file{/usr/bin/.debug/ls.debug}, and
11141 @file{/usr/lib/debug/usr/bin/ls.debug}.
11143 You can set the global debugging info directory's name, and view the
11144 name @value{GDBN} is currently using.
11148 @kindex set debug-file-directory
11149 @item set debug-file-directory @var{directory}
11150 Set the directory which @value{GDBN} searches for separate debugging
11151 information files to @var{directory}.
11153 @kindex show debug-file-directory
11154 @item show debug-file-directory
11155 Show the directory @value{GDBN} searches for separate debugging
11160 @cindex @code{.gnu_debuglink} sections
11161 @cindex debug links
11162 A debug link is a special section of the executable file named
11163 @code{.gnu_debuglink}. The section must contain:
11167 A filename, with any leading directory components removed, followed by
11170 zero to three bytes of padding, as needed to reach the next four-byte
11171 boundary within the section, and
11173 a four-byte CRC checksum, stored in the same endianness used for the
11174 executable file itself. The checksum is computed on the debugging
11175 information file's full contents by the function given below, passing
11176 zero as the @var{crc} argument.
11179 Any executable file format can carry a debug link, as long as it can
11180 contain a section named @code{.gnu_debuglink} with the contents
11183 The debugging information file itself should be an ordinary
11184 executable, containing a full set of linker symbols, sections, and
11185 debugging information. The sections of the debugging information file
11186 should have the same names, addresses and sizes as the original file,
11187 but they need not contain any data --- much like a @code{.bss} section
11188 in an ordinary executable.
11190 As of December 2002, there is no standard GNU utility to produce
11191 separated executable / debugging information file pairs. Ulrich
11192 Drepper's @file{elfutils} package, starting with version 0.53,
11193 contains a version of the @code{strip} command such that the command
11194 @kbd{strip foo -f foo.debug} removes the debugging information from
11195 the executable file @file{foo}, places it in the file
11196 @file{foo.debug}, and leaves behind a debug link in @file{foo}.
11198 Since there are many different ways to compute CRC's (different
11199 polynomials, reversals, byte ordering, etc.), the simplest way to
11200 describe the CRC used in @code{.gnu_debuglink} sections is to give the
11201 complete code for a function that computes it:
11203 @kindex gnu_debuglink_crc32
11206 gnu_debuglink_crc32 (unsigned long crc,
11207 unsigned char *buf, size_t len)
11209 static const unsigned long crc32_table[256] =
11211 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
11212 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
11213 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
11214 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
11215 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
11216 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
11217 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
11218 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
11219 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
11220 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
11221 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
11222 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
11223 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
11224 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
11225 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
11226 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
11227 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
11228 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
11229 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
11230 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
11231 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
11232 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
11233 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
11234 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
11235 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
11236 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
11237 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
11238 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
11239 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
11240 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
11241 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
11242 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
11243 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
11244 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
11245 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
11246 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
11247 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
11248 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
11249 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
11250 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
11251 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
11252 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
11253 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
11254 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
11255 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
11256 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
11257 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
11258 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
11259 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
11260 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
11261 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
11264 unsigned char *end;
11266 crc = ~crc & 0xffffffff;
11267 for (end = buf + len; buf < end; ++buf)
11268 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
11269 return ~crc & 0xffffffff;
11274 @node Symbol Errors
11275 @section Errors reading symbol files
11277 While reading a symbol file, @value{GDBN} occasionally encounters problems,
11278 such as symbol types it does not recognize, or known bugs in compiler
11279 output. By default, @value{GDBN} does not notify you of such problems, since
11280 they are relatively common and primarily of interest to people
11281 debugging compilers. If you are interested in seeing information
11282 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
11283 only one message about each such type of problem, no matter how many
11284 times the problem occurs; or you can ask @value{GDBN} to print more messages,
11285 to see how many times the problems occur, with the @code{set
11286 complaints} command (@pxref{Messages/Warnings, ,Optional warnings and
11289 The messages currently printed, and their meanings, include:
11292 @item inner block not inside outer block in @var{symbol}
11294 The symbol information shows where symbol scopes begin and end
11295 (such as at the start of a function or a block of statements). This
11296 error indicates that an inner scope block is not fully contained
11297 in its outer scope blocks.
11299 @value{GDBN} circumvents the problem by treating the inner block as if it had
11300 the same scope as the outer block. In the error message, @var{symbol}
11301 may be shown as ``@code{(don't know)}'' if the outer block is not a
11304 @item block at @var{address} out of order
11306 The symbol information for symbol scope blocks should occur in
11307 order of increasing addresses. This error indicates that it does not
11310 @value{GDBN} does not circumvent this problem, and has trouble
11311 locating symbols in the source file whose symbols it is reading. (You
11312 can often determine what source file is affected by specifying
11313 @code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and
11316 @item bad block start address patched
11318 The symbol information for a symbol scope block has a start address
11319 smaller than the address of the preceding source line. This is known
11320 to occur in the SunOS 4.1.1 (and earlier) C compiler.
11322 @value{GDBN} circumvents the problem by treating the symbol scope block as
11323 starting on the previous source line.
11325 @item bad string table offset in symbol @var{n}
11328 Symbol number @var{n} contains a pointer into the string table which is
11329 larger than the size of the string table.
11331 @value{GDBN} circumvents the problem by considering the symbol to have the
11332 name @code{foo}, which may cause other problems if many symbols end up
11335 @item unknown symbol type @code{0x@var{nn}}
11337 The symbol information contains new data types that @value{GDBN} does
11338 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
11339 uncomprehended information, in hexadecimal.
11341 @value{GDBN} circumvents the error by ignoring this symbol information.
11342 This usually allows you to debug your program, though certain symbols
11343 are not accessible. If you encounter such a problem and feel like
11344 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
11345 on @code{complain}, then go up to the function @code{read_dbx_symtab}
11346 and examine @code{*bufp} to see the symbol.
11348 @item stub type has NULL name
11350 @value{GDBN} could not find the full definition for a struct or class.
11352 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
11353 The symbol information for a C@t{++} member function is missing some
11354 information that recent versions of the compiler should have output for
11357 @item info mismatch between compiler and debugger
11359 @value{GDBN} could not parse a type specification output by the compiler.
11364 @chapter Specifying a Debugging Target
11366 @cindex debugging target
11367 A @dfn{target} is the execution environment occupied by your program.
11369 Often, @value{GDBN} runs in the same host environment as your program;
11370 in that case, the debugging target is specified as a side effect when
11371 you use the @code{file} or @code{core} commands. When you need more
11372 flexibility---for example, running @value{GDBN} on a physically separate
11373 host, or controlling a standalone system over a serial port or a
11374 realtime system over a TCP/IP connection---you can use the @code{target}
11375 command to specify one of the target types configured for @value{GDBN}
11376 (@pxref{Target Commands, ,Commands for managing targets}).
11378 @cindex target architecture
11379 It is possible to build @value{GDBN} for several different @dfn{target
11380 architectures}. When @value{GDBN} is built like that, you can choose
11381 one of the available architectures with the @kbd{set architecture}
11385 @kindex set architecture
11386 @kindex show architecture
11387 @item set architecture @var{arch}
11388 This command sets the current target architecture to @var{arch}. The
11389 value of @var{arch} can be @code{"auto"}, in addition to one of the
11390 supported architectures.
11392 @item show architecture
11393 Show the current target architecture.
11395 @item set processor
11397 @kindex set processor
11398 @kindex show processor
11399 These are alias commands for, respectively, @code{set architecture}
11400 and @code{show architecture}.
11404 * Active Targets:: Active targets
11405 * Target Commands:: Commands for managing targets
11406 * Byte Order:: Choosing target byte order
11407 * Remote:: Remote debugging
11408 * KOD:: Kernel Object Display
11412 @node Active Targets
11413 @section Active targets
11415 @cindex stacking targets
11416 @cindex active targets
11417 @cindex multiple targets
11419 There are three classes of targets: processes, core files, and
11420 executable files. @value{GDBN} can work concurrently on up to three
11421 active targets, one in each class. This allows you to (for example)
11422 start a process and inspect its activity without abandoning your work on
11425 For example, if you execute @samp{gdb a.out}, then the executable file
11426 @code{a.out} is the only active target. If you designate a core file as
11427 well---presumably from a prior run that crashed and coredumped---then
11428 @value{GDBN} has two active targets and uses them in tandem, looking
11429 first in the corefile target, then in the executable file, to satisfy
11430 requests for memory addresses. (Typically, these two classes of target
11431 are complementary, since core files contain only a program's
11432 read-write memory---variables and so on---plus machine status, while
11433 executable files contain only the program text and initialized data.)
11435 When you type @code{run}, your executable file becomes an active process
11436 target as well. When a process target is active, all @value{GDBN}
11437 commands requesting memory addresses refer to that target; addresses in
11438 an active core file or executable file target are obscured while the
11439 process target is active.
11441 Use the @code{core-file} and @code{exec-file} commands to select a new
11442 core file or executable target (@pxref{Files, ,Commands to specify
11443 files}). To specify as a target a process that is already running, use
11444 the @code{attach} command (@pxref{Attach, ,Debugging an already-running
11447 @node Target Commands
11448 @section Commands for managing targets
11451 @item target @var{type} @var{parameters}
11452 Connects the @value{GDBN} host environment to a target machine or
11453 process. A target is typically a protocol for talking to debugging
11454 facilities. You use the argument @var{type} to specify the type or
11455 protocol of the target machine.
11457 Further @var{parameters} are interpreted by the target protocol, but
11458 typically include things like device names or host names to connect
11459 with, process numbers, and baud rates.
11461 The @code{target} command does not repeat if you press @key{RET} again
11462 after executing the command.
11464 @kindex help target
11466 Displays the names of all targets available. To display targets
11467 currently selected, use either @code{info target} or @code{info files}
11468 (@pxref{Files, ,Commands to specify files}).
11470 @item help target @var{name}
11471 Describe a particular target, including any parameters necessary to
11474 @kindex set gnutarget
11475 @item set gnutarget @var{args}
11476 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
11477 knows whether it is reading an @dfn{executable},
11478 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
11479 with the @code{set gnutarget} command. Unlike most @code{target} commands,
11480 with @code{gnutarget} the @code{target} refers to a program, not a machine.
11483 @emph{Warning:} To specify a file format with @code{set gnutarget},
11484 you must know the actual BFD name.
11488 @xref{Files, , Commands to specify files}.
11490 @kindex show gnutarget
11491 @item show gnutarget
11492 Use the @code{show gnutarget} command to display what file format
11493 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
11494 @value{GDBN} will determine the file format for each file automatically,
11495 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
11498 @cindex common targets
11499 Here are some common targets (available, or not, depending on the GDB
11504 @item target exec @var{program}
11505 @cindex executable file target
11506 An executable file. @samp{target exec @var{program}} is the same as
11507 @samp{exec-file @var{program}}.
11509 @item target core @var{filename}
11510 @cindex core dump file target
11511 A core dump file. @samp{target core @var{filename}} is the same as
11512 @samp{core-file @var{filename}}.
11514 @item target remote @var{dev}
11515 @cindex remote target
11516 Remote serial target in GDB-specific protocol. The argument @var{dev}
11517 specifies what serial device to use for the connection (e.g.
11518 @file{/dev/ttya}). @xref{Remote, ,Remote debugging}. @code{target remote}
11519 supports the @code{load} command. This is only useful if you have
11520 some other way of getting the stub to the target system, and you can put
11521 it somewhere in memory where it won't get clobbered by the download.
11524 @cindex built-in simulator target
11525 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
11533 works; however, you cannot assume that a specific memory map, device
11534 drivers, or even basic I/O is available, although some simulators do
11535 provide these. For info about any processor-specific simulator details,
11536 see the appropriate section in @ref{Embedded Processors, ,Embedded
11541 Some configurations may include these targets as well:
11545 @item target nrom @var{dev}
11546 @cindex NetROM ROM emulator target
11547 NetROM ROM emulator. This target only supports downloading.
11551 Different targets are available on different configurations of @value{GDBN};
11552 your configuration may have more or fewer targets.
11554 Many remote targets require you to download the executable's code once
11555 you've successfully established a connection. You may wish to control
11556 various aspects of this process, such as the size of the data chunks
11557 used by @value{GDBN} to download program parts to the remote target.
11560 @kindex set download-write-size
11561 @item set download-write-size @var{size}
11562 Set the write size used when downloading a program. Only used when
11563 downloading a program onto a remote target. Specify zero or a
11564 negative value to disable blocked writes. The actual size of each
11565 transfer is also limited by the size of the target packet and the
11568 @kindex show download-write-size
11569 @item show download-write-size
11570 @kindex show download-write-size
11571 Show the current value of the write size.
11574 @kindex set hash@r{, for remote monitors}
11575 @cindex hash mark while downloading
11576 This command controls whether a hash mark @samp{#} is displayed while
11577 downloading a file to the remote monitor. If on, a hash mark is
11578 displayed after each S-record is successfully downloaded to the
11582 @kindex show hash@r{, for remote monitors}
11583 Show the current status of displaying the hash mark.
11585 @item set debug monitor
11586 @kindex set debug monitor
11587 @cindex display remote monitor communications
11588 Enable or disable display of communications messages between
11589 @value{GDBN} and the remote monitor.
11591 @item show debug monitor
11592 @kindex show debug monitor
11593 Show the current status of displaying communications between
11594 @value{GDBN} and the remote monitor.
11599 @kindex load @var{filename}
11600 @item load @var{filename}
11601 Depending on what remote debugging facilities are configured into
11602 @value{GDBN}, the @code{load} command may be available. Where it exists, it
11603 is meant to make @var{filename} (an executable) available for debugging
11604 on the remote system---by downloading, or dynamic linking, for example.
11605 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
11606 the @code{add-symbol-file} command.
11608 If your @value{GDBN} does not have a @code{load} command, attempting to
11609 execute it gets the error message ``@code{You can't do that when your
11610 target is @dots{}}''
11612 The file is loaded at whatever address is specified in the executable.
11613 For some object file formats, you can specify the load address when you
11614 link the program; for other formats, like a.out, the object file format
11615 specifies a fixed address.
11616 @c FIXME! This would be a good place for an xref to the GNU linker doc.
11618 @code{load} does not repeat if you press @key{RET} again after using it.
11622 @section Choosing target byte order
11624 @cindex choosing target byte order
11625 @cindex target byte order
11627 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
11628 offer the ability to run either big-endian or little-endian byte
11629 orders. Usually the executable or symbol will include a bit to
11630 designate the endian-ness, and you will not need to worry about
11631 which to use. However, you may still find it useful to adjust
11632 @value{GDBN}'s idea of processor endian-ness manually.
11636 @item set endian big
11637 Instruct @value{GDBN} to assume the target is big-endian.
11639 @item set endian little
11640 Instruct @value{GDBN} to assume the target is little-endian.
11642 @item set endian auto
11643 Instruct @value{GDBN} to use the byte order associated with the
11647 Display @value{GDBN}'s current idea of the target byte order.
11651 Note that these commands merely adjust interpretation of symbolic
11652 data on the host, and that they have absolutely no effect on the
11656 @section Remote debugging
11657 @cindex remote debugging
11659 If you are trying to debug a program running on a machine that cannot run
11660 @value{GDBN} in the usual way, it is often useful to use remote debugging.
11661 For example, you might use remote debugging on an operating system kernel,
11662 or on a small system which does not have a general purpose operating system
11663 powerful enough to run a full-featured debugger.
11665 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
11666 to make this work with particular debugging targets. In addition,
11667 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
11668 but not specific to any particular target system) which you can use if you
11669 write the remote stubs---the code that runs on the remote system to
11670 communicate with @value{GDBN}.
11672 Other remote targets may be available in your
11673 configuration of @value{GDBN}; use @code{help target} to list them.
11675 Once you've connected to the remote target, @value{GDBN} allows you to
11676 send arbitrary commands to the remote monitor:
11679 @item remote @var{command}
11680 @kindex remote@r{, a command}
11681 @cindex send command to remote monitor
11682 Send an arbitrary @var{command} string to the remote monitor.
11687 @section Kernel Object Display
11688 @cindex kernel object display
11691 Some targets support kernel object display. Using this facility,
11692 @value{GDBN} communicates specially with the underlying operating system
11693 and can display information about operating system-level objects such as
11694 mutexes and other synchronization objects. Exactly which objects can be
11695 displayed is determined on a per-OS basis.
11698 Use the @code{set os} command to set the operating system. This tells
11699 @value{GDBN} which kernel object display module to initialize:
11702 (@value{GDBP}) set os cisco
11706 The associated command @code{show os} displays the operating system
11707 set with the @code{set os} command; if no operating system has been
11708 set, @code{show os} will display an empty string @samp{""}.
11710 If @code{set os} succeeds, @value{GDBN} will display some information
11711 about the operating system, and will create a new @code{info} command
11712 which can be used to query the target. The @code{info} command is named
11713 after the operating system:
11717 (@value{GDBP}) info cisco
11718 List of Cisco Kernel Objects
11720 any Any and all objects
11723 Further subcommands can be used to query about particular objects known
11726 There is currently no way to determine whether a given operating
11727 system is supported other than to try setting it with @kbd{set os
11728 @var{name}}, where @var{name} is the name of the operating system you
11732 @node Remote Debugging
11733 @chapter Debugging remote programs
11736 * Connecting:: Connecting to a remote target
11737 * Server:: Using the gdbserver program
11738 * NetWare:: Using the gdbserve.nlm program
11739 * Remote configuration:: Remote configuration
11740 * remote stub:: Implementing a remote stub
11744 @section Connecting to a remote target
11746 On the @value{GDBN} host machine, you will need an unstripped copy of
11747 your program, since @value{GDBN} needs symobl and debugging information.
11748 Start up @value{GDBN} as usual, using the name of the local copy of your
11749 program as the first argument.
11751 @cindex serial line, @code{target remote}
11752 If you're using a serial line, you may want to give @value{GDBN} the
11753 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
11754 (@pxref{Remote configuration, set remotebaud}) before the
11755 @code{target} command.
11757 After that, use @code{target remote} to establish communications with
11758 the target machine. Its argument specifies how to communicate---either
11759 via a devicename attached to a direct serial line, or a TCP or UDP port
11760 (possibly to a terminal server which in turn has a serial line to the
11761 target). For example, to use a serial line connected to the device
11762 named @file{/dev/ttyb}:
11765 target remote /dev/ttyb
11768 @cindex TCP port, @code{target remote}
11769 To use a TCP connection, use an argument of the form
11770 @code{@var{host}:@var{port}} or @code{tcp:@var{host}:@var{port}}.
11771 For example, to connect to port 2828 on a
11772 terminal server named @code{manyfarms}:
11775 target remote manyfarms:2828
11778 If your remote target is actually running on the same machine as
11779 your debugger session (e.g.@: a simulator of your target running on
11780 the same host), you can omit the hostname. For example, to connect
11781 to port 1234 on your local machine:
11784 target remote :1234
11788 Note that the colon is still required here.
11790 @cindex UDP port, @code{target remote}
11791 To use a UDP connection, use an argument of the form
11792 @code{udp:@var{host}:@var{port}}. For example, to connect to UDP port 2828
11793 on a terminal server named @code{manyfarms}:
11796 target remote udp:manyfarms:2828
11799 When using a UDP connection for remote debugging, you should keep in mind
11800 that the `U' stands for ``Unreliable''. UDP can silently drop packets on
11801 busy or unreliable networks, which will cause havoc with your debugging
11804 Now you can use all the usual commands to examine and change data and to
11805 step and continue the remote program.
11807 @cindex interrupting remote programs
11808 @cindex remote programs, interrupting
11809 Whenever @value{GDBN} is waiting for the remote program, if you type the
11810 interrupt character (often @key{C-C}), @value{GDBN} attempts to stop the
11811 program. This may or may not succeed, depending in part on the hardware
11812 and the serial drivers the remote system uses. If you type the
11813 interrupt character once again, @value{GDBN} displays this prompt:
11816 Interrupted while waiting for the program.
11817 Give up (and stop debugging it)? (y or n)
11820 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
11821 (If you decide you want to try again later, you can use @samp{target
11822 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
11823 goes back to waiting.
11826 @kindex detach (remote)
11828 When you have finished debugging the remote program, you can use the
11829 @code{detach} command to release it from @value{GDBN} control.
11830 Detaching from the target normally resumes its execution, but the results
11831 will depend on your particular remote stub. After the @code{detach}
11832 command, @value{GDBN} is free to connect to another target.
11836 The @code{disconnect} command behaves like @code{detach}, except that
11837 the target is generally not resumed. It will wait for @value{GDBN}
11838 (this instance or another one) to connect and continue debugging. After
11839 the @code{disconnect} command, @value{GDBN} is again free to connect to
11842 @cindex send command to remote monitor
11844 @item monitor @var{cmd}
11845 This command allows you to send commands directly to the remote
11850 @section Using the @code{gdbserver} program
11853 @cindex remote connection without stubs
11854 @code{gdbserver} is a control program for Unix-like systems, which
11855 allows you to connect your program with a remote @value{GDBN} via
11856 @code{target remote}---but without linking in the usual debugging stub.
11858 @code{gdbserver} is not a complete replacement for the debugging stubs,
11859 because it requires essentially the same operating-system facilities
11860 that @value{GDBN} itself does. In fact, a system that can run
11861 @code{gdbserver} to connect to a remote @value{GDBN} could also run
11862 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
11863 because it is a much smaller program than @value{GDBN} itself. It is
11864 also easier to port than all of @value{GDBN}, so you may be able to get
11865 started more quickly on a new system by using @code{gdbserver}.
11866 Finally, if you develop code for real-time systems, you may find that
11867 the tradeoffs involved in real-time operation make it more convenient to
11868 do as much development work as possible on another system, for example
11869 by cross-compiling. You can use @code{gdbserver} to make a similar
11870 choice for debugging.
11872 @value{GDBN} and @code{gdbserver} communicate via either a serial line
11873 or a TCP connection, using the standard @value{GDBN} remote serial
11877 @item On the target machine,
11878 you need to have a copy of the program you want to debug.
11879 @code{gdbserver} does not need your program's symbol table, so you can
11880 strip the program if necessary to save space. @value{GDBN} on the host
11881 system does all the symbol handling.
11883 To use the server, you must tell it how to communicate with @value{GDBN};
11884 the name of your program; and the arguments for your program. The usual
11888 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
11891 @var{comm} is either a device name (to use a serial line) or a TCP
11892 hostname and portnumber. For example, to debug Emacs with the argument
11893 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
11897 target> gdbserver /dev/com1 emacs foo.txt
11900 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
11903 To use a TCP connection instead of a serial line:
11906 target> gdbserver host:2345 emacs foo.txt
11909 The only difference from the previous example is the first argument,
11910 specifying that you are communicating with the host @value{GDBN} via
11911 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
11912 expect a TCP connection from machine @samp{host} to local TCP port 2345.
11913 (Currently, the @samp{host} part is ignored.) You can choose any number
11914 you want for the port number as long as it does not conflict with any
11915 TCP ports already in use on the target system (for example, @code{23} is
11916 reserved for @code{telnet}).@footnote{If you choose a port number that
11917 conflicts with another service, @code{gdbserver} prints an error message
11918 and exits.} You must use the same port number with the host @value{GDBN}
11919 @code{target remote} command.
11921 On some targets, @code{gdbserver} can also attach to running programs.
11922 This is accomplished via the @code{--attach} argument. The syntax is:
11925 target> gdbserver @var{comm} --attach @var{pid}
11928 @var{pid} is the process ID of a currently running process. It isn't necessary
11929 to point @code{gdbserver} at a binary for the running process.
11932 @cindex attach to a program by name
11933 You can debug processes by name instead of process ID if your target has the
11934 @code{pidof} utility:
11937 target> gdbserver @var{comm} --attach `pidof @var{PROGRAM}`
11940 In case more than one copy of @var{PROGRAM} is running, or @var{PROGRAM}
11941 has multiple threads, most versions of @code{pidof} support the
11942 @code{-s} option to only return the first process ID.
11944 @item On the host machine,
11945 connect to your target (@pxref{Connecting,,Connecting to a remote target}).
11946 For TCP connections, you must start up @code{gdbserver} prior to using
11947 the @code{target remote} command. Otherwise you may get an error whose
11948 text depends on the host system, but which usually looks something like
11949 @samp{Connection refused}. You don't need to use the @code{load}
11950 command in @value{GDBN} when using @code{gdbserver}, since the program is
11951 already on the target. However, if you want to load the symbols (as
11952 you normally would), do that with the @code{file} command, and issue
11953 it @emph{before} connecting to the server; otherwise, you will get an
11954 error message saying @code{"Program is already running"}, since the
11955 program is considered running after the connection.
11960 @section Using the @code{gdbserve.nlm} program
11962 @kindex gdbserve.nlm
11963 @code{gdbserve.nlm} is a control program for NetWare systems, which
11964 allows you to connect your program with a remote @value{GDBN} via
11965 @code{target remote}.
11967 @value{GDBN} and @code{gdbserve.nlm} communicate via a serial line,
11968 using the standard @value{GDBN} remote serial protocol.
11971 @item On the target machine,
11972 you need to have a copy of the program you want to debug.
11973 @code{gdbserve.nlm} does not need your program's symbol table, so you
11974 can strip the program if necessary to save space. @value{GDBN} on the
11975 host system does all the symbol handling.
11977 To use the server, you must tell it how to communicate with
11978 @value{GDBN}; the name of your program; and the arguments for your
11979 program. The syntax is:
11982 load gdbserve [ BOARD=@var{board} ] [ PORT=@var{port} ]
11983 [ BAUD=@var{baud} ] @var{program} [ @var{args} @dots{} ]
11986 @var{board} and @var{port} specify the serial line; @var{baud} specifies
11987 the baud rate used by the connection. @var{port} and @var{node} default
11988 to 0, @var{baud} defaults to 9600@dmn{bps}.
11990 For example, to debug Emacs with the argument @samp{foo.txt}and
11991 communicate with @value{GDBN} over serial port number 2 or board 1
11992 using a 19200@dmn{bps} connection:
11995 load gdbserve BOARD=1 PORT=2 BAUD=19200 emacs foo.txt
11999 On the @value{GDBN} host machine, connect to your target (@pxref{Connecting,,
12000 Connecting to a remote target}).
12004 @node Remote configuration
12005 @section Remote configuration
12008 @kindex show remote
12009 This section documents the configuration options available when
12010 debugging remote programs. For the options related to the File I/O
12011 extensions of the remote protocol, see @ref{The system call,
12012 system-call-allowed}.
12015 @item set remoteaddresssize @var{bits}
12016 @cindex adress size for remote targets
12017 @cindex bits in remote address
12018 Set the maximum size of address in a memory packet to the specified
12019 number of bits. @value{GDBN} will mask off the address bits above
12020 that number, when it passes addresses to the remote target. The
12021 default value is the number of bits in the target's address.
12023 @item show remoteaddresssize
12024 Show the current value of remote address size in bits.
12026 @item set remotebaud @var{n}
12027 @cindex baud rate for remote targets
12028 Set the baud rate for the remote serial I/O to @var{n} baud. The
12029 value is used to set the speed of the serial port used for debugging
12032 @item show remotebaud
12033 Show the current speed of the remote connection.
12035 @item set remotebreak
12036 @cindex interrupt remote programs
12037 @cindex BREAK signal instead of Ctrl-C
12038 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
12039 when you press the @key{Ctrl-C} key to interrupt the program running
12040 on the remote. If set to off, @value{GDBN} sends the @samp{Strl-C}
12041 character instead. The default is off, since most remote systems
12042 expect to see @samp{Ctrl-C} as the interrupt signal.
12044 @item show remotebreak
12045 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
12046 interrupt the remote program.
12048 @item set remotedebug
12049 @cindex debug remote protocol
12050 @cindex remote protocol debugging
12051 @cindex display remote packets
12052 Control the debugging of the remote protocol. When enabled, each
12053 packet sent to or received from the remote target is displayed. The
12056 @item show remotedebug
12057 Show the current setting of the remote protocol debugging.
12059 @item set remotedevice @var{device}
12060 @cindex serial port name
12061 Set the name of the serial port through which to communicate to the
12062 remote target to @var{device}. This is the device used by
12063 @value{GDBN} to open the serial communications line to the remote
12064 target. There's no default, so you must set a valid port name for the
12065 remote serial communications to work. (Some varieties of the
12066 @code{target} command accept the port name as part of their
12069 @item show remotedevice
12070 Show the current name of the serial port.
12072 @item set remotelogbase @var{base}
12073 Set the base (a.k.a.@: radix) of logging serial protocol
12074 communications to @var{base}. Supported values of @var{base} are:
12075 @code{ascii}, @code{octal}, and @code{hex}. The default is
12078 @item show remotelogbase
12079 Show the current setting of the radix for logging remote serial
12082 @item set remotelogfile @var{file}
12083 @cindex record serial communications on file
12084 Record remote serial communications on the named @var{file}. The
12085 default is not to record at all.
12087 @item show remotelogfile.
12088 Show the current setting of the file name on which to record the
12089 serial communications.
12091 @item set remotetimeout @var{num}
12092 @cindex timeout for serial communications
12093 @cindex remote timeout
12094 Set the timeout limit to wait for the remote target to respond to
12095 @var{num} seconds. The default is 2 seconds.
12097 @item show remotetimeout
12098 Show the current number of seconds to wait for the remote target
12101 @cindex limit hardware breakpoints and watchpoints
12102 @cindex remote target, limit break- and watchpoints
12103 @anchor{set remote hardware-watchpoint-limit}
12104 @anchor{set remote hardware-breakpoint-limit}
12105 @item set remote hardware-watchpoint-limit @var{limit}
12106 @itemx set remote hardware-breakpoint-limit @var{limit}
12107 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
12108 watchpoints. A limit of -1, the default, is treated as unlimited.
12110 @item set remote fetch-register-packet
12111 @itemx set remote set-register-packet
12112 @itemx set remote P-packet
12113 @itemx set remote p-packet
12115 @cindex fetch registers from remote targets
12116 @cindex set registers in remote targets
12117 Determine whether @value{GDBN} can set and fetch registers from the
12118 remote target using the @samp{P} packets. The default depends on the
12119 remote stub's support of the @samp{P} packets (@value{GDBN} queries
12120 the stub when this packet is first required).
12122 @item show remote fetch-register-packet
12123 @itemx show remote set-register-packet
12124 @itemx show remote P-packet
12125 @itemx show remote p-packet
12126 Show the current setting of using the @samp{P} packets for setting and
12127 fetching registers from the remote target.
12129 @cindex binary downloads
12131 @item set remote binary-download-packet
12132 @itemx set remote X-packet
12133 Determine whether @value{GDBN} sends downloads in binary mode using
12134 the @samp{X} packets. The default is on.
12136 @item show remote binary-download-packet
12137 @itemx show remote X-packet
12138 Show the current setting of using the @samp{X} packets for binary
12141 @item set remote read-aux-vector-packet
12142 @cindex auxiliary vector of remote target
12143 @cindex @code{auxv}, and remote targets
12144 Set the use of the remote protocol's @samp{qPart:auxv:read} (target
12145 auxiliary vector read) request. This request is used to fetch the
12146 remote target's @dfn{auxiliary vector}, see @ref{OS Information,
12147 Auxiliary Vector}. The default setting depends on the remote stub's
12148 support of this request (@value{GDBN} queries the stub when this
12149 request is first required). @xref{General Query Packets, qPart}, for
12150 more information about this request.
12152 @item show remote read-aux-vector-packet
12153 Show the current setting of use of the @samp{qPart:auxv:read} request.
12155 @item set remote symbol-lookup-packet
12156 @cindex remote symbol lookup request
12157 Set the use of the remote protocol's @samp{qSymbol} (target symbol
12158 lookup) request. This request is used to communicate symbol
12159 information to the remote target, e.g., whenever a new shared library
12160 is loaded by the remote (@pxref{Files, shared libraries}). The
12161 default setting depends on the remote stub's support of this request
12162 (@value{GDBN} queries the stub when this request is first required).
12163 @xref{General Query Packets, qSymbol}, for more information about this
12166 @item show remote symbol-lookup-packet
12167 Show the current setting of use of the @samp{qSymbol} request.
12169 @item set remote verbose-resume-packet
12170 @cindex resume remote target
12171 @cindex signal thread, and remote targets
12172 @cindex single-step thread, and remote targets
12173 @cindex thread-specific operations on remote targets
12174 Set the use of the remote protocol's @samp{vCont} (descriptive resume)
12175 request. This request is used to resume specific threads in the
12176 remote target, and to single-step or signal them. The default setting
12177 depends on the remote stub's support of this request (@value{GDBN}
12178 queries the stub when this request is first required). This setting
12179 affects debugging of multithreaded programs: if @samp{vCont} cannot be
12180 used, @value{GDBN} might be unable to single-step a specific thread,
12181 especially under @code{set scheduler-locking off}; it is also
12182 impossible to pause a specific thread. @xref{Packets, vCont}, for
12185 @item show remote verbose-resume-packet
12186 Show the current setting of use of the @samp{vCont} request
12188 @item set remote software-breakpoint-packet
12189 @itemx set remote hardware-breakpoint-packet
12190 @itemx set remote write-watchpoint-packet
12191 @itemx set remote read-watchpoint-packet
12192 @itemx set remote access-watchpoint-packet
12193 @itemx set remote Z-packet
12195 @cindex remote hardware breakpoints and watchpoints
12196 These commands enable or disable the use of @samp{Z} packets for
12197 setting breakpoints and watchpoints in the remote target. The default
12198 depends on the remote stub's support of the @samp{Z} packets
12199 (@value{GDBN} queries the stub when each packet is first required).
12200 The command @code{set remote Z-packet}, kept for back-compatibility,
12201 turns on or off all the features that require the use of @samp{Z}
12204 @item show remote software-breakpoint-packet
12205 @itemx show remote hardware-breakpoint-packet
12206 @itemx show remote write-watchpoint-packet
12207 @itemx show remote read-watchpoint-packet
12208 @itemx show remote access-watchpoint-packet
12209 @itemx show remote Z-packet
12210 Show the current setting of @samp{Z} packets usage.
12212 @item set remote get-thread-local-storage-address
12213 @kindex set remote get-thread-local-storage-address
12214 @cindex thread local storage of remote targets
12215 This command enables or disables the use of the @samp{qGetTLSAddr}
12216 (Get Thread Local Storage Address) request packet. The default
12217 depends on whether the remote stub supports this request.
12218 @xref{General Query Packets, qGetTLSAddr}, for more details about this
12221 @item show remote get-thread-local-storage-address
12222 @kindex show remote get-thread-local-storage-address
12223 Show the current setting of @samp{qGetTLSAddr} packet usage.
12227 @section Implementing a remote stub
12229 @cindex debugging stub, example
12230 @cindex remote stub, example
12231 @cindex stub example, remote debugging
12232 The stub files provided with @value{GDBN} implement the target side of the
12233 communication protocol, and the @value{GDBN} side is implemented in the
12234 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
12235 these subroutines to communicate, and ignore the details. (If you're
12236 implementing your own stub file, you can still ignore the details: start
12237 with one of the existing stub files. @file{sparc-stub.c} is the best
12238 organized, and therefore the easiest to read.)
12240 @cindex remote serial debugging, overview
12241 To debug a program running on another machine (the debugging
12242 @dfn{target} machine), you must first arrange for all the usual
12243 prerequisites for the program to run by itself. For example, for a C
12248 A startup routine to set up the C runtime environment; these usually
12249 have a name like @file{crt0}. The startup routine may be supplied by
12250 your hardware supplier, or you may have to write your own.
12253 A C subroutine library to support your program's
12254 subroutine calls, notably managing input and output.
12257 A way of getting your program to the other machine---for example, a
12258 download program. These are often supplied by the hardware
12259 manufacturer, but you may have to write your own from hardware
12263 The next step is to arrange for your program to use a serial port to
12264 communicate with the machine where @value{GDBN} is running (the @dfn{host}
12265 machine). In general terms, the scheme looks like this:
12269 @value{GDBN} already understands how to use this protocol; when everything
12270 else is set up, you can simply use the @samp{target remote} command
12271 (@pxref{Targets,,Specifying a Debugging Target}).
12273 @item On the target,
12274 you must link with your program a few special-purpose subroutines that
12275 implement the @value{GDBN} remote serial protocol. The file containing these
12276 subroutines is called a @dfn{debugging stub}.
12278 On certain remote targets, you can use an auxiliary program
12279 @code{gdbserver} instead of linking a stub into your program.
12280 @xref{Server,,Using the @code{gdbserver} program}, for details.
12283 The debugging stub is specific to the architecture of the remote
12284 machine; for example, use @file{sparc-stub.c} to debug programs on
12287 @cindex remote serial stub list
12288 These working remote stubs are distributed with @value{GDBN}:
12293 @cindex @file{i386-stub.c}
12296 For Intel 386 and compatible architectures.
12299 @cindex @file{m68k-stub.c}
12300 @cindex Motorola 680x0
12302 For Motorola 680x0 architectures.
12305 @cindex @file{sh-stub.c}
12308 For Renesas SH architectures.
12311 @cindex @file{sparc-stub.c}
12313 For @sc{sparc} architectures.
12315 @item sparcl-stub.c
12316 @cindex @file{sparcl-stub.c}
12319 For Fujitsu @sc{sparclite} architectures.
12323 The @file{README} file in the @value{GDBN} distribution may list other
12324 recently added stubs.
12327 * Stub Contents:: What the stub can do for you
12328 * Bootstrapping:: What you must do for the stub
12329 * Debug Session:: Putting it all together
12332 @node Stub Contents
12333 @subsection What the stub can do for you
12335 @cindex remote serial stub
12336 The debugging stub for your architecture supplies these three
12340 @item set_debug_traps
12341 @findex set_debug_traps
12342 @cindex remote serial stub, initialization
12343 This routine arranges for @code{handle_exception} to run when your
12344 program stops. You must call this subroutine explicitly near the
12345 beginning of your program.
12347 @item handle_exception
12348 @findex handle_exception
12349 @cindex remote serial stub, main routine
12350 This is the central workhorse, but your program never calls it
12351 explicitly---the setup code arranges for @code{handle_exception} to
12352 run when a trap is triggered.
12354 @code{handle_exception} takes control when your program stops during
12355 execution (for example, on a breakpoint), and mediates communications
12356 with @value{GDBN} on the host machine. This is where the communications
12357 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
12358 representative on the target machine. It begins by sending summary
12359 information on the state of your program, then continues to execute,
12360 retrieving and transmitting any information @value{GDBN} needs, until you
12361 execute a @value{GDBN} command that makes your program resume; at that point,
12362 @code{handle_exception} returns control to your own code on the target
12366 @cindex @code{breakpoint} subroutine, remote
12367 Use this auxiliary subroutine to make your program contain a
12368 breakpoint. Depending on the particular situation, this may be the only
12369 way for @value{GDBN} to get control. For instance, if your target
12370 machine has some sort of interrupt button, you won't need to call this;
12371 pressing the interrupt button transfers control to
12372 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
12373 simply receiving characters on the serial port may also trigger a trap;
12374 again, in that situation, you don't need to call @code{breakpoint} from
12375 your own program---simply running @samp{target remote} from the host
12376 @value{GDBN} session gets control.
12378 Call @code{breakpoint} if none of these is true, or if you simply want
12379 to make certain your program stops at a predetermined point for the
12380 start of your debugging session.
12383 @node Bootstrapping
12384 @subsection What you must do for the stub
12386 @cindex remote stub, support routines
12387 The debugging stubs that come with @value{GDBN} are set up for a particular
12388 chip architecture, but they have no information about the rest of your
12389 debugging target machine.
12391 First of all you need to tell the stub how to communicate with the
12395 @item int getDebugChar()
12396 @findex getDebugChar
12397 Write this subroutine to read a single character from the serial port.
12398 It may be identical to @code{getchar} for your target system; a
12399 different name is used to allow you to distinguish the two if you wish.
12401 @item void putDebugChar(int)
12402 @findex putDebugChar
12403 Write this subroutine to write a single character to the serial port.
12404 It may be identical to @code{putchar} for your target system; a
12405 different name is used to allow you to distinguish the two if you wish.
12408 @cindex control C, and remote debugging
12409 @cindex interrupting remote targets
12410 If you want @value{GDBN} to be able to stop your program while it is
12411 running, you need to use an interrupt-driven serial driver, and arrange
12412 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
12413 character). That is the character which @value{GDBN} uses to tell the
12414 remote system to stop.
12416 Getting the debugging target to return the proper status to @value{GDBN}
12417 probably requires changes to the standard stub; one quick and dirty way
12418 is to just execute a breakpoint instruction (the ``dirty'' part is that
12419 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
12421 Other routines you need to supply are:
12424 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
12425 @findex exceptionHandler
12426 Write this function to install @var{exception_address} in the exception
12427 handling tables. You need to do this because the stub does not have any
12428 way of knowing what the exception handling tables on your target system
12429 are like (for example, the processor's table might be in @sc{rom},
12430 containing entries which point to a table in @sc{ram}).
12431 @var{exception_number} is the exception number which should be changed;
12432 its meaning is architecture-dependent (for example, different numbers
12433 might represent divide by zero, misaligned access, etc). When this
12434 exception occurs, control should be transferred directly to
12435 @var{exception_address}, and the processor state (stack, registers,
12436 and so on) should be just as it is when a processor exception occurs. So if
12437 you want to use a jump instruction to reach @var{exception_address}, it
12438 should be a simple jump, not a jump to subroutine.
12440 For the 386, @var{exception_address} should be installed as an interrupt
12441 gate so that interrupts are masked while the handler runs. The gate
12442 should be at privilege level 0 (the most privileged level). The
12443 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
12444 help from @code{exceptionHandler}.
12446 @item void flush_i_cache()
12447 @findex flush_i_cache
12448 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
12449 instruction cache, if any, on your target machine. If there is no
12450 instruction cache, this subroutine may be a no-op.
12452 On target machines that have instruction caches, @value{GDBN} requires this
12453 function to make certain that the state of your program is stable.
12457 You must also make sure this library routine is available:
12460 @item void *memset(void *, int, int)
12462 This is the standard library function @code{memset} that sets an area of
12463 memory to a known value. If you have one of the free versions of
12464 @code{libc.a}, @code{memset} can be found there; otherwise, you must
12465 either obtain it from your hardware manufacturer, or write your own.
12468 If you do not use the GNU C compiler, you may need other standard
12469 library subroutines as well; this varies from one stub to another,
12470 but in general the stubs are likely to use any of the common library
12471 subroutines which @code{@value{GCC}} generates as inline code.
12474 @node Debug Session
12475 @subsection Putting it all together
12477 @cindex remote serial debugging summary
12478 In summary, when your program is ready to debug, you must follow these
12483 Make sure you have defined the supporting low-level routines
12484 (@pxref{Bootstrapping,,What you must do for the stub}):
12486 @code{getDebugChar}, @code{putDebugChar},
12487 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
12491 Insert these lines near the top of your program:
12499 For the 680x0 stub only, you need to provide a variable called
12500 @code{exceptionHook}. Normally you just use:
12503 void (*exceptionHook)() = 0;
12507 but if before calling @code{set_debug_traps}, you set it to point to a
12508 function in your program, that function is called when
12509 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
12510 error). The function indicated by @code{exceptionHook} is called with
12511 one parameter: an @code{int} which is the exception number.
12514 Compile and link together: your program, the @value{GDBN} debugging stub for
12515 your target architecture, and the supporting subroutines.
12518 Make sure you have a serial connection between your target machine and
12519 the @value{GDBN} host, and identify the serial port on the host.
12522 @c The "remote" target now provides a `load' command, so we should
12523 @c document that. FIXME.
12524 Download your program to your target machine (or get it there by
12525 whatever means the manufacturer provides), and start it.
12528 Start @value{GDBN} on the host, and connect to the target
12529 (@pxref{Connecting,,Connecting to a remote target}).
12533 @node Configurations
12534 @chapter Configuration-Specific Information
12536 While nearly all @value{GDBN} commands are available for all native and
12537 cross versions of the debugger, there are some exceptions. This chapter
12538 describes things that are only available in certain configurations.
12540 There are three major categories of configurations: native
12541 configurations, where the host and target are the same, embedded
12542 operating system configurations, which are usually the same for several
12543 different processor architectures, and bare embedded processors, which
12544 are quite different from each other.
12549 * Embedded Processors::
12556 This section describes details specific to particular native
12561 * BSD libkvm Interface:: Debugging BSD kernel memory images
12562 * SVR4 Process Information:: SVR4 process information
12563 * DJGPP Native:: Features specific to the DJGPP port
12564 * Cygwin Native:: Features specific to the Cygwin port
12565 * Hurd Native:: Features specific to @sc{gnu} Hurd
12566 * Neutrino:: Features specific to QNX Neutrino
12572 On HP-UX systems, if you refer to a function or variable name that
12573 begins with a dollar sign, @value{GDBN} searches for a user or system
12574 name first, before it searches for a convenience variable.
12577 @node BSD libkvm Interface
12578 @subsection BSD libkvm Interface
12581 @cindex kernel memory image
12582 @cindex kernel crash dump
12584 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
12585 interface that provides a uniform interface for accessing kernel virtual
12586 memory images, including live systems and crash dumps. @value{GDBN}
12587 uses this interface to allow you to debug live kernels and kernel crash
12588 dumps on many native BSD configurations. This is implemented as a
12589 special @code{kvm} debugging target. For debugging a live system, load
12590 the currently running kernel into @value{GDBN} and connect to the
12594 (@value{GDBP}) @b{target kvm}
12597 For debugging crash dumps, provide the file name of the crash dump as an
12601 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
12604 Once connected to the @code{kvm} target, the following commands are
12610 Set current context from the @dfn{Process Control Block} (PCB) address.
12613 Set current context from proc address. This command isn't available on
12614 modern FreeBSD systems.
12617 @node SVR4 Process Information
12618 @subsection SVR4 process information
12620 @cindex examine process image
12621 @cindex process info via @file{/proc}
12623 Many versions of SVR4 and compatible systems provide a facility called
12624 @samp{/proc} that can be used to examine the image of a running
12625 process using file-system subroutines. If @value{GDBN} is configured
12626 for an operating system with this facility, the command @code{info
12627 proc} is available to report information about the process running
12628 your program, or about any process running on your system. @code{info
12629 proc} works only on SVR4 systems that include the @code{procfs} code.
12630 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
12631 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
12637 @itemx info proc @var{process-id}
12638 Summarize available information about any running process. If a
12639 process ID is specified by @var{process-id}, display information about
12640 that process; otherwise display information about the program being
12641 debugged. The summary includes the debugged process ID, the command
12642 line used to invoke it, its current working directory, and its
12643 executable file's absolute file name.
12645 On some systems, @var{process-id} can be of the form
12646 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
12647 within a process. If the optional @var{pid} part is missing, it means
12648 a thread from the process being debugged (the leading @samp{/} still
12649 needs to be present, or else @value{GDBN} will interpret the number as
12650 a process ID rather than a thread ID).
12652 @item info proc mappings
12653 @cindex memory address space mappings
12654 Report the memory address space ranges accessible in the program, with
12655 information on whether the process has read, write, or execute access
12656 rights to each range. On @sc{gnu}/Linux systems, each memory range
12657 includes the object file which is mapped to that range, instead of the
12658 memory access rights to that range.
12660 @item info proc stat
12661 @itemx info proc status
12662 @cindex process detailed status information
12663 These subcommands are specific to @sc{gnu}/Linux systems. They show
12664 the process-related information, including the user ID and group ID;
12665 how many threads are there in the process; its virtual memory usage;
12666 the signals that are pending, blocked, and ignored; its TTY; its
12667 consumption of system and user time; its stack size; its @samp{nice}
12668 value; etc. For more information, see the @samp{proc} man page
12669 (type @kbd{man 5 proc} from your shell prompt).
12671 @item info proc all
12672 Show all the information about the process described under all of the
12673 above @code{info proc} subcommands.
12676 @comment These sub-options of 'info proc' were not included when
12677 @comment procfs.c was re-written. Keep their descriptions around
12678 @comment against the day when someone finds the time to put them back in.
12679 @kindex info proc times
12680 @item info proc times
12681 Starting time, user CPU time, and system CPU time for your program and
12684 @kindex info proc id
12686 Report on the process IDs related to your program: its own process ID,
12687 the ID of its parent, the process group ID, and the session ID.
12690 @item set procfs-trace
12691 @kindex set procfs-trace
12692 @cindex @code{procfs} API calls
12693 This command enables and disables tracing of @code{procfs} API calls.
12695 @item show procfs-trace
12696 @kindex show procfs-trace
12697 Show the current state of @code{procfs} API call tracing.
12699 @item set procfs-file @var{file}
12700 @kindex set procfs-file
12701 Tell @value{GDBN} to write @code{procfs} API trace to the named
12702 @var{file}. @value{GDBN} appends the trace info to the previous
12703 contents of the file. The default is to display the trace on the
12706 @item show procfs-file
12707 @kindex show procfs-file
12708 Show the file to which @code{procfs} API trace is written.
12710 @item proc-trace-entry
12711 @itemx proc-trace-exit
12712 @itemx proc-untrace-entry
12713 @itemx proc-untrace-exit
12714 @kindex proc-trace-entry
12715 @kindex proc-trace-exit
12716 @kindex proc-untrace-entry
12717 @kindex proc-untrace-exit
12718 These commands enable and disable tracing of entries into and exits
12719 from the @code{syscall} interface.
12722 @kindex info pidlist
12723 @cindex process list, QNX Neutrino
12724 For QNX Neutrino only, this command displays the list of all the
12725 processes and all the threads within each process.
12728 @kindex info meminfo
12729 @cindex mapinfo list, QNX Neutrino
12730 For QNX Neutrino only, this command displays the list of all mapinfos.
12734 @subsection Features for Debugging @sc{djgpp} Programs
12735 @cindex @sc{djgpp} debugging
12736 @cindex native @sc{djgpp} debugging
12737 @cindex MS-DOS-specific commands
12740 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
12741 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
12742 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
12743 top of real-mode DOS systems and their emulations.
12745 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
12746 defines a few commands specific to the @sc{djgpp} port. This
12747 subsection describes those commands.
12752 This is a prefix of @sc{djgpp}-specific commands which print
12753 information about the target system and important OS structures.
12756 @cindex MS-DOS system info
12757 @cindex free memory information (MS-DOS)
12758 @item info dos sysinfo
12759 This command displays assorted information about the underlying
12760 platform: the CPU type and features, the OS version and flavor, the
12761 DPMI version, and the available conventional and DPMI memory.
12766 @cindex segment descriptor tables
12767 @cindex descriptor tables display
12769 @itemx info dos ldt
12770 @itemx info dos idt
12771 These 3 commands display entries from, respectively, Global, Local,
12772 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
12773 tables are data structures which store a descriptor for each segment
12774 that is currently in use. The segment's selector is an index into a
12775 descriptor table; the table entry for that index holds the
12776 descriptor's base address and limit, and its attributes and access
12779 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
12780 segment (used for both data and the stack), and a DOS segment (which
12781 allows access to DOS/BIOS data structures and absolute addresses in
12782 conventional memory). However, the DPMI host will usually define
12783 additional segments in order to support the DPMI environment.
12785 @cindex garbled pointers
12786 These commands allow to display entries from the descriptor tables.
12787 Without an argument, all entries from the specified table are
12788 displayed. An argument, which should be an integer expression, means
12789 display a single entry whose index is given by the argument. For
12790 example, here's a convenient way to display information about the
12791 debugged program's data segment:
12794 @exdent @code{(@value{GDBP}) info dos ldt $ds}
12795 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
12799 This comes in handy when you want to see whether a pointer is outside
12800 the data segment's limit (i.e.@: @dfn{garbled}).
12802 @cindex page tables display (MS-DOS)
12804 @itemx info dos pte
12805 These two commands display entries from, respectively, the Page
12806 Directory and the Page Tables. Page Directories and Page Tables are
12807 data structures which control how virtual memory addresses are mapped
12808 into physical addresses. A Page Table includes an entry for every
12809 page of memory that is mapped into the program's address space; there
12810 may be several Page Tables, each one holding up to 4096 entries. A
12811 Page Directory has up to 4096 entries, one each for every Page Table
12812 that is currently in use.
12814 Without an argument, @kbd{info dos pde} displays the entire Page
12815 Directory, and @kbd{info dos pte} displays all the entries in all of
12816 the Page Tables. An argument, an integer expression, given to the
12817 @kbd{info dos pde} command means display only that entry from the Page
12818 Directory table. An argument given to the @kbd{info dos pte} command
12819 means display entries from a single Page Table, the one pointed to by
12820 the specified entry in the Page Directory.
12822 @cindex direct memory access (DMA) on MS-DOS
12823 These commands are useful when your program uses @dfn{DMA} (Direct
12824 Memory Access), which needs physical addresses to program the DMA
12827 These commands are supported only with some DPMI servers.
12829 @cindex physical address from linear address
12830 @item info dos address-pte @var{addr}
12831 This command displays the Page Table entry for a specified linear
12832 address. The argument @var{addr} is a linear address which should
12833 already have the appropriate segment's base address added to it,
12834 because this command accepts addresses which may belong to @emph{any}
12835 segment. For example, here's how to display the Page Table entry for
12836 the page where a variable @code{i} is stored:
12839 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
12840 @exdent @code{Page Table entry for address 0x11a00d30:}
12841 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
12845 This says that @code{i} is stored at offset @code{0xd30} from the page
12846 whose physical base address is @code{0x02698000}, and shows all the
12847 attributes of that page.
12849 Note that you must cast the addresses of variables to a @code{char *},
12850 since otherwise the value of @code{__djgpp_base_address}, the base
12851 address of all variables and functions in a @sc{djgpp} program, will
12852 be added using the rules of C pointer arithmetics: if @code{i} is
12853 declared an @code{int}, @value{GDBN} will add 4 times the value of
12854 @code{__djgpp_base_address} to the address of @code{i}.
12856 Here's another example, it displays the Page Table entry for the
12860 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
12861 @exdent @code{Page Table entry for address 0x29110:}
12862 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
12866 (The @code{+ 3} offset is because the transfer buffer's address is the
12867 3rd member of the @code{_go32_info_block} structure.) The output
12868 clearly shows that this DPMI server maps the addresses in conventional
12869 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
12870 linear (@code{0x29110}) addresses are identical.
12872 This command is supported only with some DPMI servers.
12875 @cindex DOS serial data link, remote debugging
12876 In addition to native debugging, the DJGPP port supports remote
12877 debugging via a serial data link. The following commands are specific
12878 to remote serial debugging in the DJGPP port of @value{GDBN}.
12881 @kindex set com1base
12882 @kindex set com1irq
12883 @kindex set com2base
12884 @kindex set com2irq
12885 @kindex set com3base
12886 @kindex set com3irq
12887 @kindex set com4base
12888 @kindex set com4irq
12889 @item set com1base @var{addr}
12890 This command sets the base I/O port address of the @file{COM1} serial
12893 @item set com1irq @var{irq}
12894 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
12895 for the @file{COM1} serial port.
12897 There are similar commands @samp{set com2base}, @samp{set com3irq},
12898 etc.@: for setting the port address and the @code{IRQ} lines for the
12901 @kindex show com1base
12902 @kindex show com1irq
12903 @kindex show com2base
12904 @kindex show com2irq
12905 @kindex show com3base
12906 @kindex show com3irq
12907 @kindex show com4base
12908 @kindex show com4irq
12909 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
12910 display the current settings of the base address and the @code{IRQ}
12911 lines used by the COM ports.
12914 @kindex info serial
12915 @cindex DOS serial port status
12916 This command prints the status of the 4 DOS serial ports. For each
12917 port, it prints whether it's active or not, its I/O base address and
12918 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
12919 counts of various errors encountered so far.
12923 @node Cygwin Native
12924 @subsection Features for Debugging MS Windows PE executables
12925 @cindex MS Windows debugging
12926 @cindex native Cygwin debugging
12927 @cindex Cygwin-specific commands
12929 @value{GDBN} supports native debugging of MS Windows programs, including
12930 DLLs with and without symbolic debugging information. There are various
12931 additional Cygwin-specific commands, described in this subsection. The
12932 subsubsection @pxref{Non-debug DLL symbols} describes working with DLLs
12933 that have no debugging symbols.
12939 This is a prefix of MS Windows specific commands which print
12940 information about the target system and important OS structures.
12942 @item info w32 selector
12943 This command displays information returned by
12944 the Win32 API @code{GetThreadSelectorEntry} function.
12945 It takes an optional argument that is evaluated to
12946 a long value to give the information about this given selector.
12947 Without argument, this command displays information
12948 about the the six segment registers.
12952 This is a Cygwin specific alias of info shared.
12954 @kindex dll-symbols
12956 This command loads symbols from a dll similarly to
12957 add-sym command but without the need to specify a base address.
12959 @kindex set new-console
12960 @item set new-console @var{mode}
12961 If @var{mode} is @code{on} the debuggee will
12962 be started in a new console on next start.
12963 If @var{mode} is @code{off}i, the debuggee will
12964 be started in the same console as the debugger.
12966 @kindex show new-console
12967 @item show new-console
12968 Displays whether a new console is used
12969 when the debuggee is started.
12971 @kindex set new-group
12972 @item set new-group @var{mode}
12973 This boolean value controls whether the debuggee should
12974 start a new group or stay in the same group as the debugger.
12975 This affects the way the Windows OS handles
12978 @kindex show new-group
12979 @item show new-group
12980 Displays current value of new-group boolean.
12982 @kindex set debugevents
12983 @item set debugevents
12984 This boolean value adds debug output concerning events seen by the debugger.
12986 @kindex set debugexec
12987 @item set debugexec
12988 This boolean value adds debug output concerning execute events
12989 seen by the debugger.
12991 @kindex set debugexceptions
12992 @item set debugexceptions
12993 This boolean value adds debug ouptut concerning exception events
12994 seen by the debugger.
12996 @kindex set debugmemory
12997 @item set debugmemory
12998 This boolean value adds debug ouptut concerning memory events
12999 seen by the debugger.
13003 This boolean values specifies whether the debuggee is called
13004 via a shell or directly (default value is on).
13008 Displays if the debuggee will be started with a shell.
13013 * Non-debug DLL symbols:: Support for DLLs without debugging symbols
13016 @node Non-debug DLL symbols
13017 @subsubsection Support for DLLs without debugging symbols
13018 @cindex DLLs with no debugging symbols
13019 @cindex Minimal symbols and DLLs
13021 Very often on windows, some of the DLLs that your program relies on do
13022 not include symbolic debugging information (for example,
13023 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
13024 symbols in a DLL, it relies on the minimal amount of symbolic
13025 information contained in the DLL's export table. This subsubsection
13026 describes working with such symbols, known internally to @value{GDBN} as
13027 ``minimal symbols''.
13029 Note that before the debugged program has started execution, no DLLs
13030 will have been loaded. The easiest way around this problem is simply to
13031 start the program --- either by setting a breakpoint or letting the
13032 program run once to completion. It is also possible to force
13033 @value{GDBN} to load a particular DLL before starting the executable ---
13034 see the shared library information in @pxref{Files} or the
13035 @code{dll-symbols} command in @pxref{Cygwin Native}. Currently,
13036 explicitly loading symbols from a DLL with no debugging information will
13037 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
13038 which may adversely affect symbol lookup performance.
13040 @subsubsection DLL name prefixes
13042 In keeping with the naming conventions used by the Microsoft debugging
13043 tools, DLL export symbols are made available with a prefix based on the
13044 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
13045 also entered into the symbol table, so @code{CreateFileA} is often
13046 sufficient. In some cases there will be name clashes within a program
13047 (particularly if the executable itself includes full debugging symbols)
13048 necessitating the use of the fully qualified name when referring to the
13049 contents of the DLL. Use single-quotes around the name to avoid the
13050 exclamation mark (``!'') being interpreted as a language operator.
13052 Note that the internal name of the DLL may be all upper-case, even
13053 though the file name of the DLL is lower-case, or vice-versa. Since
13054 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
13055 some confusion. If in doubt, try the @code{info functions} and
13056 @code{info variables} commands or even @code{maint print msymbols} (see
13057 @pxref{Symbols}). Here's an example:
13060 (@value{GDBP}) info function CreateFileA
13061 All functions matching regular expression "CreateFileA":
13063 Non-debugging symbols:
13064 0x77e885f4 CreateFileA
13065 0x77e885f4 KERNEL32!CreateFileA
13069 (@value{GDBP}) info function !
13070 All functions matching regular expression "!":
13072 Non-debugging symbols:
13073 0x6100114c cygwin1!__assert
13074 0x61004034 cygwin1!_dll_crt0@@0
13075 0x61004240 cygwin1!dll_crt0(per_process *)
13079 @subsubsection Working with minimal symbols
13081 Symbols extracted from a DLL's export table do not contain very much
13082 type information. All that @value{GDBN} can do is guess whether a symbol
13083 refers to a function or variable depending on the linker section that
13084 contains the symbol. Also note that the actual contents of the memory
13085 contained in a DLL are not available unless the program is running. This
13086 means that you cannot examine the contents of a variable or disassemble
13087 a function within a DLL without a running program.
13089 Variables are generally treated as pointers and dereferenced
13090 automatically. For this reason, it is often necessary to prefix a
13091 variable name with the address-of operator (``&'') and provide explicit
13092 type information in the command. Here's an example of the type of
13096 (@value{GDBP}) print 'cygwin1!__argv'
13101 (@value{GDBP}) x 'cygwin1!__argv'
13102 0x10021610: "\230y\""
13105 And two possible solutions:
13108 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
13109 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
13113 (@value{GDBP}) x/2x &'cygwin1!__argv'
13114 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
13115 (@value{GDBP}) x/x 0x10021608
13116 0x10021608: 0x0022fd98
13117 (@value{GDBP}) x/s 0x0022fd98
13118 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
13121 Setting a break point within a DLL is possible even before the program
13122 starts execution. However, under these circumstances, @value{GDBN} can't
13123 examine the initial instructions of the function in order to skip the
13124 function's frame set-up code. You can work around this by using ``*&''
13125 to set the breakpoint at a raw memory address:
13128 (@value{GDBP}) break *&'python22!PyOS_Readline'
13129 Breakpoint 1 at 0x1e04eff0
13132 The author of these extensions is not entirely convinced that setting a
13133 break point within a shared DLL like @file{kernel32.dll} is completely
13137 @subsection Commands specific to @sc{gnu} Hurd systems
13138 @cindex @sc{gnu} Hurd debugging
13140 This subsection describes @value{GDBN} commands specific to the
13141 @sc{gnu} Hurd native debugging.
13146 @kindex set signals@r{, Hurd command}
13147 @kindex set sigs@r{, Hurd command}
13148 This command toggles the state of inferior signal interception by
13149 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
13150 affected by this command. @code{sigs} is a shorthand alias for
13155 @kindex show signals@r{, Hurd command}
13156 @kindex show sigs@r{, Hurd command}
13157 Show the current state of intercepting inferior's signals.
13159 @item set signal-thread
13160 @itemx set sigthread
13161 @kindex set signal-thread
13162 @kindex set sigthread
13163 This command tells @value{GDBN} which thread is the @code{libc} signal
13164 thread. That thread is run when a signal is delivered to a running
13165 process. @code{set sigthread} is the shorthand alias of @code{set
13168 @item show signal-thread
13169 @itemx show sigthread
13170 @kindex show signal-thread
13171 @kindex show sigthread
13172 These two commands show which thread will run when the inferior is
13173 delivered a signal.
13176 @kindex set stopped@r{, Hurd command}
13177 This commands tells @value{GDBN} that the inferior process is stopped,
13178 as with the @code{SIGSTOP} signal. The stopped process can be
13179 continued by delivering a signal to it.
13182 @kindex show stopped@r{, Hurd command}
13183 This command shows whether @value{GDBN} thinks the debuggee is
13186 @item set exceptions
13187 @kindex set exceptions@r{, Hurd command}
13188 Use this command to turn off trapping of exceptions in the inferior.
13189 When exception trapping is off, neither breakpoints nor
13190 single-stepping will work. To restore the default, set exception
13193 @item show exceptions
13194 @kindex show exceptions@r{, Hurd command}
13195 Show the current state of trapping exceptions in the inferior.
13197 @item set task pause
13198 @kindex set task@r{, Hurd commands}
13199 @cindex task attributes (@sc{gnu} Hurd)
13200 @cindex pause current task (@sc{gnu} Hurd)
13201 This command toggles task suspension when @value{GDBN} has control.
13202 Setting it to on takes effect immediately, and the task is suspended
13203 whenever @value{GDBN} gets control. Setting it to off will take
13204 effect the next time the inferior is continued. If this option is set
13205 to off, you can use @code{set thread default pause on} or @code{set
13206 thread pause on} (see below) to pause individual threads.
13208 @item show task pause
13209 @kindex show task@r{, Hurd commands}
13210 Show the current state of task suspension.
13212 @item set task detach-suspend-count
13213 @cindex task suspend count
13214 @cindex detach from task, @sc{gnu} Hurd
13215 This command sets the suspend count the task will be left with when
13216 @value{GDBN} detaches from it.
13218 @item show task detach-suspend-count
13219 Show the suspend count the task will be left with when detaching.
13221 @item set task exception-port
13222 @itemx set task excp
13223 @cindex task exception port, @sc{gnu} Hurd
13224 This command sets the task exception port to which @value{GDBN} will
13225 forward exceptions. The argument should be the value of the @dfn{send
13226 rights} of the task. @code{set task excp} is a shorthand alias.
13228 @item set noninvasive
13229 @cindex noninvasive task options
13230 This command switches @value{GDBN} to a mode that is the least
13231 invasive as far as interfering with the inferior is concerned. This
13232 is the same as using @code{set task pause}, @code{set exceptions}, and
13233 @code{set signals} to values opposite to the defaults.
13235 @item info send-rights
13236 @itemx info receive-rights
13237 @itemx info port-rights
13238 @itemx info port-sets
13239 @itemx info dead-names
13242 @cindex send rights, @sc{gnu} Hurd
13243 @cindex receive rights, @sc{gnu} Hurd
13244 @cindex port rights, @sc{gnu} Hurd
13245 @cindex port sets, @sc{gnu} Hurd
13246 @cindex dead names, @sc{gnu} Hurd
13247 These commands display information about, respectively, send rights,
13248 receive rights, port rights, port sets, and dead names of a task.
13249 There are also shorthand aliases: @code{info ports} for @code{info
13250 port-rights} and @code{info psets} for @code{info port-sets}.
13252 @item set thread pause
13253 @kindex set thread@r{, Hurd command}
13254 @cindex thread properties, @sc{gnu} Hurd
13255 @cindex pause current thread (@sc{gnu} Hurd)
13256 This command toggles current thread suspension when @value{GDBN} has
13257 control. Setting it to on takes effect immediately, and the current
13258 thread is suspended whenever @value{GDBN} gets control. Setting it to
13259 off will take effect the next time the inferior is continued.
13260 Normally, this command has no effect, since when @value{GDBN} has
13261 control, the whole task is suspended. However, if you used @code{set
13262 task pause off} (see above), this command comes in handy to suspend
13263 only the current thread.
13265 @item show thread pause
13266 @kindex show thread@r{, Hurd command}
13267 This command shows the state of current thread suspension.
13269 @item set thread run
13270 This comamnd sets whether the current thread is allowed to run.
13272 @item show thread run
13273 Show whether the current thread is allowed to run.
13275 @item set thread detach-suspend-count
13276 @cindex thread suspend count, @sc{gnu} Hurd
13277 @cindex detach from thread, @sc{gnu} Hurd
13278 This command sets the suspend count @value{GDBN} will leave on a
13279 thread when detaching. This number is relative to the suspend count
13280 found by @value{GDBN} when it notices the thread; use @code{set thread
13281 takeover-suspend-count} to force it to an absolute value.
13283 @item show thread detach-suspend-count
13284 Show the suspend count @value{GDBN} will leave on the thread when
13287 @item set thread exception-port
13288 @itemx set thread excp
13289 Set the thread exception port to which to forward exceptions. This
13290 overrides the port set by @code{set task exception-port} (see above).
13291 @code{set thread excp} is the shorthand alias.
13293 @item set thread takeover-suspend-count
13294 Normally, @value{GDBN}'s thread suspend counts are relative to the
13295 value @value{GDBN} finds when it notices each thread. This command
13296 changes the suspend counts to be absolute instead.
13298 @item set thread default
13299 @itemx show thread default
13300 @cindex thread default settings, @sc{gnu} Hurd
13301 Each of the above @code{set thread} commands has a @code{set thread
13302 default} counterpart (e.g., @code{set thread default pause}, @code{set
13303 thread default exception-port}, etc.). The @code{thread default}
13304 variety of commands sets the default thread properties for all
13305 threads; you can then change the properties of individual threads with
13306 the non-default commands.
13311 @subsection QNX Neutrino
13312 @cindex QNX Neutrino
13314 @value{GDBN} provides the following commands specific to the QNX
13318 @item set debug nto-debug
13319 @kindex set debug nto-debug
13320 When set to on, enables debugging messages specific to the QNX
13323 @item show debug nto-debug
13324 @kindex show debug nto-debug
13325 Show the current state of QNX Neutrino messages.
13330 @section Embedded Operating Systems
13332 This section describes configurations involving the debugging of
13333 embedded operating systems that are available for several different
13337 * VxWorks:: Using @value{GDBN} with VxWorks
13340 @value{GDBN} includes the ability to debug programs running on
13341 various real-time operating systems.
13344 @subsection Using @value{GDBN} with VxWorks
13350 @kindex target vxworks
13351 @item target vxworks @var{machinename}
13352 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
13353 is the target system's machine name or IP address.
13357 On VxWorks, @code{load} links @var{filename} dynamically on the
13358 current target system as well as adding its symbols in @value{GDBN}.
13360 @value{GDBN} enables developers to spawn and debug tasks running on networked
13361 VxWorks targets from a Unix host. Already-running tasks spawned from
13362 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
13363 both the Unix host and on the VxWorks target. The program
13364 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
13365 installed with the name @code{vxgdb}, to distinguish it from a
13366 @value{GDBN} for debugging programs on the host itself.)
13369 @item VxWorks-timeout @var{args}
13370 @kindex vxworks-timeout
13371 All VxWorks-based targets now support the option @code{vxworks-timeout}.
13372 This option is set by the user, and @var{args} represents the number of
13373 seconds @value{GDBN} waits for responses to rpc's. You might use this if
13374 your VxWorks target is a slow software simulator or is on the far side
13375 of a thin network line.
13378 The following information on connecting to VxWorks was current when
13379 this manual was produced; newer releases of VxWorks may use revised
13382 @findex INCLUDE_RDB
13383 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
13384 to include the remote debugging interface routines in the VxWorks
13385 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
13386 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
13387 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
13388 source debugging task @code{tRdbTask} when VxWorks is booted. For more
13389 information on configuring and remaking VxWorks, see the manufacturer's
13391 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
13393 Once you have included @file{rdb.a} in your VxWorks system image and set
13394 your Unix execution search path to find @value{GDBN}, you are ready to
13395 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
13396 @code{vxgdb}, depending on your installation).
13398 @value{GDBN} comes up showing the prompt:
13405 * VxWorks Connection:: Connecting to VxWorks
13406 * VxWorks Download:: VxWorks download
13407 * VxWorks Attach:: Running tasks
13410 @node VxWorks Connection
13411 @subsubsection Connecting to VxWorks
13413 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
13414 network. To connect to a target whose host name is ``@code{tt}'', type:
13417 (vxgdb) target vxworks tt
13421 @value{GDBN} displays messages like these:
13424 Attaching remote machine across net...
13429 @value{GDBN} then attempts to read the symbol tables of any object modules
13430 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
13431 these files by searching the directories listed in the command search
13432 path (@pxref{Environment, ,Your program's environment}); if it fails
13433 to find an object file, it displays a message such as:
13436 prog.o: No such file or directory.
13439 When this happens, add the appropriate directory to the search path with
13440 the @value{GDBN} command @code{path}, and execute the @code{target}
13443 @node VxWorks Download
13444 @subsubsection VxWorks download
13446 @cindex download to VxWorks
13447 If you have connected to the VxWorks target and you want to debug an
13448 object that has not yet been loaded, you can use the @value{GDBN}
13449 @code{load} command to download a file from Unix to VxWorks
13450 incrementally. The object file given as an argument to the @code{load}
13451 command is actually opened twice: first by the VxWorks target in order
13452 to download the code, then by @value{GDBN} in order to read the symbol
13453 table. This can lead to problems if the current working directories on
13454 the two systems differ. If both systems have NFS mounted the same
13455 filesystems, you can avoid these problems by using absolute paths.
13456 Otherwise, it is simplest to set the working directory on both systems
13457 to the directory in which the object file resides, and then to reference
13458 the file by its name, without any path. For instance, a program
13459 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
13460 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
13461 program, type this on VxWorks:
13464 -> cd "@var{vxpath}/vw/demo/rdb"
13468 Then, in @value{GDBN}, type:
13471 (vxgdb) cd @var{hostpath}/vw/demo/rdb
13472 (vxgdb) load prog.o
13475 @value{GDBN} displays a response similar to this:
13478 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
13481 You can also use the @code{load} command to reload an object module
13482 after editing and recompiling the corresponding source file. Note that
13483 this makes @value{GDBN} delete all currently-defined breakpoints,
13484 auto-displays, and convenience variables, and to clear the value
13485 history. (This is necessary in order to preserve the integrity of
13486 debugger's data structures that reference the target system's symbol
13489 @node VxWorks Attach
13490 @subsubsection Running tasks
13492 @cindex running VxWorks tasks
13493 You can also attach to an existing task using the @code{attach} command as
13497 (vxgdb) attach @var{task}
13501 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
13502 or suspended when you attach to it. Running tasks are suspended at
13503 the time of attachment.
13505 @node Embedded Processors
13506 @section Embedded Processors
13508 This section goes into details specific to particular embedded
13511 @cindex send command to simulator
13512 Whenever a specific embedded processor has a simulator, @value{GDBN}
13513 allows to send an arbitrary command to the simulator.
13516 @item sim @var{command}
13517 @kindex sim@r{, a command}
13518 Send an arbitrary @var{command} string to the simulator. Consult the
13519 documentation for the specific simulator in use for information about
13520 acceptable commands.
13526 * H8/300:: Renesas H8/300
13527 * H8/500:: Renesas H8/500
13528 * M32R/D:: Renesas M32R/D
13529 * M68K:: Motorola M68K
13530 * MIPS Embedded:: MIPS Embedded
13531 * OpenRISC 1000:: OpenRisc 1000
13532 * PA:: HP PA Embedded
13535 * Sparclet:: Tsqware Sparclet
13536 * Sparclite:: Fujitsu Sparclite
13537 * ST2000:: Tandem ST2000
13538 * Z8000:: Zilog Z8000
13541 * Super-H:: Renesas Super-H
13542 * WinCE:: Windows CE child processes
13551 @item target rdi @var{dev}
13552 ARM Angel monitor, via RDI library interface to ADP protocol. You may
13553 use this target to communicate with both boards running the Angel
13554 monitor, or with the EmbeddedICE JTAG debug device.
13557 @item target rdp @var{dev}
13562 @value{GDBN} provides the following ARM-specific commands:
13565 @item set arm disassembler
13567 This commands selects from a list of disassembly styles. The
13568 @code{"std"} style is the standard style.
13570 @item show arm disassembler
13572 Show the current disassembly style.
13574 @item set arm apcs32
13575 @cindex ARM 32-bit mode
13576 This command toggles ARM operation mode between 32-bit and 26-bit.
13578 @item show arm apcs32
13579 Display the current usage of the ARM 32-bit mode.
13581 @item set arm fpu @var{fputype}
13582 This command sets the ARM floating-point unit (FPU) type. The
13583 argument @var{fputype} can be one of these:
13587 Determine the FPU type by querying the OS ABI.
13589 Software FPU, with mixed-endian doubles on little-endian ARM
13592 GCC-compiled FPA co-processor.
13594 Software FPU with pure-endian doubles.
13600 Show the current type of the FPU.
13603 This command forces @value{GDBN} to use the specified ABI.
13606 Show the currently used ABI.
13608 @item set debug arm
13609 Toggle whether to display ARM-specific debugging messages from the ARM
13610 target support subsystem.
13612 @item show debug arm
13613 Show whether ARM-specific debugging messages are enabled.
13616 The following commands are available when an ARM target is debugged
13617 using the RDI interface:
13620 @item rdilogfile @r{[}@var{file}@r{]}
13622 @cindex ADP (Angel Debugger Protocol) logging
13623 Set the filename for the ADP (Angel Debugger Protocol) packet log.
13624 With an argument, sets the log file to the specified @var{file}. With
13625 no argument, show the current log file name. The default log file is
13628 @item rdilogenable @r{[}@var{arg}@r{]}
13629 @kindex rdilogenable
13630 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
13631 enables logging, with an argument 0 or @code{"no"} disables it. With
13632 no arguments displays the current setting. When logging is enabled,
13633 ADP packets exchanged between @value{GDBN} and the RDI target device
13634 are logged to a file.
13636 @item set rdiromatzero
13637 @kindex set rdiromatzero
13638 @cindex ROM at zero address, RDI
13639 Tell @value{GDBN} whether the target has ROM at address 0. If on,
13640 vector catching is disabled, so that zero address can be used. If off
13641 (the default), vector catching is enabled. For this command to take
13642 effect, it needs to be invoked prior to the @code{target rdi} command.
13644 @item show rdiromatzero
13645 @kindex show rdiromatzero
13646 Show the current setting of ROM at zero address.
13648 @item set rdiheartbeat
13649 @kindex set rdiheartbeat
13650 @cindex RDI heartbeat
13651 Enable or disable RDI heartbeat packets. It is not recommended to
13652 turn on this option, since it confuses ARM and EPI JTAG interface, as
13653 well as the Angel monitor.
13655 @item show rdiheartbeat
13656 @kindex show rdiheartbeat
13657 Show the setting of RDI heartbeat packets.
13662 @subsection Renesas H8/300
13666 @kindex target hms@r{, with H8/300}
13667 @item target hms @var{dev}
13668 A Renesas SH, H8/300, or H8/500 board, attached via serial line to your host.
13669 Use special commands @code{device} and @code{speed} to control the serial
13670 line and the communications speed used.
13672 @kindex target e7000@r{, with H8/300}
13673 @item target e7000 @var{dev}
13674 E7000 emulator for Renesas H8 and SH.
13676 @kindex target sh3@r{, with H8/300}
13677 @kindex target sh3e@r{, with H8/300}
13678 @item target sh3 @var{dev}
13679 @itemx target sh3e @var{dev}
13680 Renesas SH-3 and SH-3E target systems.
13684 @cindex download to H8/300 or H8/500
13685 @cindex H8/300 or H8/500 download
13686 @cindex download to Renesas SH
13687 @cindex Renesas SH download
13688 When you select remote debugging to a Renesas SH, H8/300, or H8/500
13689 board, the @code{load} command downloads your program to the Renesas
13690 board and also opens it as the current executable target for
13691 @value{GDBN} on your host (like the @code{file} command).
13693 @value{GDBN} needs to know these things to talk to your
13694 Renesas SH, H8/300, or H8/500:
13698 that you want to use @samp{target hms}, the remote debugging interface
13699 for Renesas microprocessors, or @samp{target e7000}, the in-circuit
13700 emulator for the Renesas SH and the Renesas 300H. (@samp{target hms} is
13701 the default when @value{GDBN} is configured specifically for the Renesas SH,
13702 H8/300, or H8/500.)
13705 what serial device connects your host to your Renesas board (the first
13706 serial device available on your host is the default).
13709 what speed to use over the serial device.
13713 * Renesas Boards:: Connecting to Renesas boards.
13714 * Renesas ICE:: Using the E7000 In-Circuit Emulator.
13715 * Renesas Special:: Special @value{GDBN} commands for Renesas micros.
13718 @node Renesas Boards
13719 @subsubsection Connecting to Renesas boards
13721 @c only for Unix hosts
13723 @cindex serial device, Renesas micros
13724 Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you
13725 need to explicitly set the serial device. The default @var{port} is the
13726 first available port on your host. This is only necessary on Unix
13727 hosts, where it is typically something like @file{/dev/ttya}.
13730 @cindex serial line speed, Renesas micros
13731 @code{@value{GDBN}} has another special command to set the communications
13732 speed: @samp{speed @var{bps}}. This command also is only used from Unix
13733 hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with
13734 the DOS @code{mode} command (for instance,
13735 @w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection).
13737 The @samp{device} and @samp{speed} commands are available only when you
13738 use a Unix host to debug your Renesas microprocessor programs. If you
13740 @value{GDBN} depends on an auxiliary terminate-and-stay-resident program
13741 called @code{asynctsr} to communicate with the development board
13742 through a PC serial port. You must also use the DOS @code{mode} command
13743 to set up the serial port on the DOS side.
13745 The following sample session illustrates the steps needed to start a
13746 program under @value{GDBN} control on an H8/300. The example uses a
13747 sample H8/300 program called @file{t.x}. The procedure is the same for
13748 the Renesas SH and the H8/500.
13750 First hook up your development board. In this example, we use a
13751 board attached to serial port @code{COM2}; if you use a different serial
13752 port, substitute its name in the argument of the @code{mode} command.
13753 When you call @code{asynctsr}, the auxiliary comms program used by the
13754 debugger, you give it just the numeric part of the serial port's name;
13755 for example, @samp{asyncstr 2} below runs @code{asyncstr} on
13759 C:\H8300\TEST> asynctsr 2
13760 C:\H8300\TEST> mode com2:9600,n,8,1,p
13762 Resident portion of MODE loaded
13764 COM2: 9600, n, 8, 1, p
13769 @emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
13770 @code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
13771 disable it, or even boot without it, to use @code{asynctsr} to control
13772 your development board.
13775 @kindex target hms@r{, and serial protocol}
13776 Now that serial communications are set up, and the development board is
13777 connected, you can start up @value{GDBN}. Call @code{@value{GDBN}} with
13778 the name of your program as the argument. @code{@value{GDBN}} prompts
13779 you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
13780 commands to begin your debugging session: @samp{target hms} to specify
13781 cross-debugging to the Renesas board, and the @code{load} command to
13782 download your program to the board. @code{load} displays the names of
13783 the program's sections, and a @samp{*} for each 2K of data downloaded.
13784 (If you want to refresh @value{GDBN} data on symbols or on the
13785 executable file without downloading, use the @value{GDBN} commands
13786 @code{file} or @code{symbol-file}. These commands, and @code{load}
13787 itself, are described in @ref{Files,,Commands to specify files}.)
13790 (eg-C:\H8300\TEST) @value{GDBP} t.x
13791 @value{GDBN} is free software and you are welcome to distribute copies
13792 of it under certain conditions; type "show copying" to see
13794 There is absolutely no warranty for @value{GDBN}; type "show warranty"
13796 @value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
13797 (@value{GDBP}) target hms
13798 Connected to remote H8/300 HMS system.
13799 (@value{GDBP}) load t.x
13800 .text : 0x8000 .. 0xabde ***********
13801 .data : 0xabde .. 0xad30 *
13802 .stack : 0xf000 .. 0xf014 *
13805 At this point, you're ready to run or debug your program. From here on,
13806 you can use all the usual @value{GDBN} commands. The @code{break} command
13807 sets breakpoints; the @code{run} command starts your program;
13808 @code{print} or @code{x} display data; the @code{continue} command
13809 resumes execution after stopping at a breakpoint. You can use the
13810 @code{help} command at any time to find out more about @value{GDBN} commands.
13812 Remember, however, that @emph{operating system} facilities aren't
13813 available on your development board; for example, if your program hangs,
13814 you can't send an interrupt---but you can press the @sc{reset} switch!
13816 Use the @sc{reset} button on the development board
13819 to interrupt your program (don't use @kbd{ctl-C} on the DOS host---it has
13820 no way to pass an interrupt signal to the development board); and
13823 to return to the @value{GDBN} command prompt after your program finishes
13824 normally. The communications protocol provides no other way for @value{GDBN}
13825 to detect program completion.
13828 In either case, @value{GDBN} sees the effect of a @sc{reset} on the
13829 development board as a ``normal exit'' of your program.
13832 @subsubsection Using the E7000 in-circuit emulator
13834 @kindex target e7000@r{, with Renesas ICE}
13835 You can use the E7000 in-circuit emulator to develop code for either the
13836 Renesas SH or the H8/300H. Use one of these forms of the @samp{target
13837 e7000} command to connect @value{GDBN} to your E7000:
13840 @item target e7000 @var{port} @var{speed}
13841 Use this form if your E7000 is connected to a serial port. The
13842 @var{port} argument identifies what serial port to use (for example,
13843 @samp{com2}). The third argument is the line speed in bits per second
13844 (for example, @samp{9600}).
13846 @item target e7000 @var{hostname}
13847 If your E7000 is installed as a host on a TCP/IP network, you can just
13848 specify its hostname; @value{GDBN} uses @code{telnet} to connect.
13851 The following special commands are available when debugging with the
13855 @item e7000 @var{command}
13857 @cindex send command to E7000 monitor
13858 This sends the specified @var{command} to the E7000 monitor.
13860 @item ftplogin @var{machine} @var{username} @var{password} @var{dir}
13861 @kindex ftplogin@r{, E7000}
13862 This command records information for subsequent interface with the
13863 E7000 monitor via the FTP protocol: @value{GDBN} will log into the
13864 named @var{machine} using specified @var{username} and @var{password},
13865 and then chdir to the named directory @var{dir}.
13867 @item ftpload @var{file}
13868 @kindex ftpload@r{, E7000}
13869 This command uses credentials recorded by @code{ftplogin} to fetch and
13870 load the named @var{file} from the E7000 monitor.
13873 @kindex drain@r{, E7000}
13874 This command drains any pending text buffers stored on the E7000.
13876 @item set usehardbreakpoints
13877 @itemx show usehardbreakpoints
13878 @kindex set usehardbreakpoints@r{, E7000}
13879 @kindex show usehardbreakpoints@r{, E7000}
13880 @cindex hardware breakpoints, and E7000
13881 These commands set and show the use of hardware breakpoints for all
13882 breakpoints. @xref{Set Breaks, hardware-assisted breakpoint}, for
13883 more information about using hardware breakpoints selectively.
13886 @node Renesas Special
13887 @subsubsection Special @value{GDBN} commands for Renesas micros
13889 Some @value{GDBN} commands are available only for the H8/300:
13893 @kindex set machine
13894 @kindex show machine
13895 @item set machine h8300
13896 @itemx set machine h8300h
13897 Condition @value{GDBN} for one of the two variants of the H8/300
13898 architecture with @samp{set machine}. You can use @samp{show machine}
13899 to check which variant is currently in effect.
13908 @kindex set memory @var{mod}
13909 @cindex memory models, H8/500
13910 @item set memory @var{mod}
13912 Specify which H8/500 memory model (@var{mod}) you are using with
13913 @samp{set memory}; check which memory model is in effect with @samp{show
13914 memory}. The accepted values for @var{mod} are @code{small},
13915 @code{big}, @code{medium}, and @code{compact}.
13920 @subsection Renesas M32R/D and M32R/SDI
13923 @kindex target m32r
13924 @item target m32r @var{dev}
13925 Renesas M32R/D ROM monitor.
13927 @kindex target m32rsdi
13928 @item target m32rsdi @var{dev}
13929 Renesas M32R SDI server, connected via parallel port to the board.
13932 The following @value{GDBN} commands are specific to the M32R monitor:
13935 @item set download-path @var{path}
13936 @kindex set download-path
13937 @cindex find downloadable @sc{srec} files (M32R)
13938 Set the default path for finding donwloadable @sc{srec} files.
13940 @item show download-path
13941 @kindex show download-path
13942 Show the default path for downloadable @sc{srec} files.
13944 @item set board-address @var{addr}
13945 @kindex set board-address
13946 @cindex M32-EVA target board address
13947 Set the IP address for the M32R-EVA target board.
13949 @item show board-address
13950 @kindex show board-address
13951 Show the current IP address of the target board.
13953 @item set server-address @var{addr}
13954 @kindex set server-address
13955 @cindex download server address (M32R)
13956 Set the IP address for the download server, which is the @value{GDBN}'s
13959 @item show server-address
13960 @kindex show server-address
13961 Display the IP address of the download server.
13963 @item upload @r{[}@var{file}@r{]}
13964 @kindex upload@r{, M32R}
13965 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
13966 upload capability. If no @var{file} argument is given, the current
13967 executable file is uploaded.
13969 @item tload @r{[}@var{file}@r{]}
13970 @kindex tload@r{, M32R}
13971 Test the @code{upload} command.
13974 The following commands are available for M32R/SDI:
13979 @cindex reset SDI connection, M32R
13980 This command resets the SDI connection.
13984 This command shows the SDI connection status.
13987 @kindex debug_chaos
13988 @cindex M32R/Chaos debugging
13989 Instructs the remote that M32R/Chaos debugging is to be used.
13991 @item use_debug_dma
13992 @kindex use_debug_dma
13993 Instructs the remote to use the DEBUG_DMA method of accessing memory.
13996 @kindex use_mon_code
13997 Instructs the remote to use the MON_CODE method of accessing memory.
14000 @kindex use_ib_break
14001 Instructs the remote to set breakpoints by IB break.
14003 @item use_dbt_break
14004 @kindex use_dbt_break
14005 Instructs the remote to set breakpoints by DBT.
14011 The Motorola m68k configuration includes ColdFire support, and
14012 target command for the following ROM monitors.
14016 @kindex target abug
14017 @item target abug @var{dev}
14018 ABug ROM monitor for M68K.
14020 @kindex target cpu32bug
14021 @item target cpu32bug @var{dev}
14022 CPU32BUG monitor, running on a CPU32 (M68K) board.
14024 @kindex target dbug
14025 @item target dbug @var{dev}
14026 dBUG ROM monitor for Motorola ColdFire.
14029 @item target est @var{dev}
14030 EST-300 ICE monitor, running on a CPU32 (M68K) board.
14032 @kindex target rom68k
14033 @item target rom68k @var{dev}
14034 ROM 68K monitor, running on an M68K IDP board.
14040 @kindex target rombug
14041 @item target rombug @var{dev}
14042 ROMBUG ROM monitor for OS/9000.
14046 @node MIPS Embedded
14047 @subsection MIPS Embedded
14049 @cindex MIPS boards
14050 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
14051 MIPS board attached to a serial line. This is available when
14052 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
14055 Use these @value{GDBN} commands to specify the connection to your target board:
14058 @item target mips @var{port}
14059 @kindex target mips @var{port}
14060 To run a program on the board, start up @code{@value{GDBP}} with the
14061 name of your program as the argument. To connect to the board, use the
14062 command @samp{target mips @var{port}}, where @var{port} is the name of
14063 the serial port connected to the board. If the program has not already
14064 been downloaded to the board, you may use the @code{load} command to
14065 download it. You can then use all the usual @value{GDBN} commands.
14067 For example, this sequence connects to the target board through a serial
14068 port, and loads and runs a program called @var{prog} through the
14072 host$ @value{GDBP} @var{prog}
14073 @value{GDBN} is free software and @dots{}
14074 (@value{GDBP}) target mips /dev/ttyb
14075 (@value{GDBP}) load @var{prog}
14079 @item target mips @var{hostname}:@var{portnumber}
14080 On some @value{GDBN} host configurations, you can specify a TCP
14081 connection (for instance, to a serial line managed by a terminal
14082 concentrator) instead of a serial port, using the syntax
14083 @samp{@var{hostname}:@var{portnumber}}.
14085 @item target pmon @var{port}
14086 @kindex target pmon @var{port}
14089 @item target ddb @var{port}
14090 @kindex target ddb @var{port}
14091 NEC's DDB variant of PMON for Vr4300.
14093 @item target lsi @var{port}
14094 @kindex target lsi @var{port}
14095 LSI variant of PMON.
14097 @kindex target r3900
14098 @item target r3900 @var{dev}
14099 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
14101 @kindex target array
14102 @item target array @var{dev}
14103 Array Tech LSI33K RAID controller board.
14109 @value{GDBN} also supports these special commands for MIPS targets:
14112 @item set mipsfpu double
14113 @itemx set mipsfpu single
14114 @itemx set mipsfpu none
14115 @itemx set mipsfpu auto
14116 @itemx show mipsfpu
14117 @kindex set mipsfpu
14118 @kindex show mipsfpu
14119 @cindex MIPS remote floating point
14120 @cindex floating point, MIPS remote
14121 If your target board does not support the MIPS floating point
14122 coprocessor, you should use the command @samp{set mipsfpu none} (if you
14123 need this, you may wish to put the command in your @value{GDBN} init
14124 file). This tells @value{GDBN} how to find the return value of
14125 functions which return floating point values. It also allows
14126 @value{GDBN} to avoid saving the floating point registers when calling
14127 functions on the board. If you are using a floating point coprocessor
14128 with only single precision floating point support, as on the @sc{r4650}
14129 processor, use the command @samp{set mipsfpu single}. The default
14130 double precision floating point coprocessor may be selected using
14131 @samp{set mipsfpu double}.
14133 In previous versions the only choices were double precision or no
14134 floating point, so @samp{set mipsfpu on} will select double precision
14135 and @samp{set mipsfpu off} will select no floating point.
14137 As usual, you can inquire about the @code{mipsfpu} variable with
14138 @samp{show mipsfpu}.
14140 @item set timeout @var{seconds}
14141 @itemx set retransmit-timeout @var{seconds}
14142 @itemx show timeout
14143 @itemx show retransmit-timeout
14144 @cindex @code{timeout}, MIPS protocol
14145 @cindex @code{retransmit-timeout}, MIPS protocol
14146 @kindex set timeout
14147 @kindex show timeout
14148 @kindex set retransmit-timeout
14149 @kindex show retransmit-timeout
14150 You can control the timeout used while waiting for a packet, in the MIPS
14151 remote protocol, with the @code{set timeout @var{seconds}} command. The
14152 default is 5 seconds. Similarly, you can control the timeout used while
14153 waiting for an acknowledgement of a packet with the @code{set
14154 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
14155 You can inspect both values with @code{show timeout} and @code{show
14156 retransmit-timeout}. (These commands are @emph{only} available when
14157 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
14159 The timeout set by @code{set timeout} does not apply when @value{GDBN}
14160 is waiting for your program to stop. In that case, @value{GDBN} waits
14161 forever because it has no way of knowing how long the program is going
14162 to run before stopping.
14164 @item set syn-garbage-limit @var{num}
14165 @kindex set syn-garbage-limit@r{, MIPS remote}
14166 @cindex synchronize with remote MIPS target
14167 Limit the maximum number of characters @value{GDBN} should ignore when
14168 it tries to synchronize with the remote target. The default is 10
14169 characters. Setting the limit to -1 means there's no limit.
14171 @item show syn-garbage-limit
14172 @kindex show syn-garbage-limit@r{, MIPS remote}
14173 Show the current limit on the number of characters to ignore when
14174 trying to synchronize with the remote system.
14176 @item set monitor-prompt @var{prompt}
14177 @kindex set monitor-prompt@r{, MIPS remote}
14178 @cindex remote monitor prompt
14179 Tell @value{GDBN} to expect the specified @var{prompt} string from the
14180 remote monitor. The default depends on the target:
14190 @item show monitor-prompt
14191 @kindex show monitor-prompt@r{, MIPS remote}
14192 Show the current strings @value{GDBN} expects as the prompt from the
14195 @item set monitor-warnings
14196 @kindex set monitor-warnings@r{, MIPS remote}
14197 Enable or disable monitor warnings about hardware breakpoints. This
14198 has effect only for the @code{lsi} target. When on, @value{GDBN} will
14199 display warning messages whose codes are returned by the @code{lsi}
14200 PMON monitor for breakpoint commands.
14202 @item show monitor-warnings
14203 @kindex show monitor-warnings@r{, MIPS remote}
14204 Show the current setting of printing monitor warnings.
14206 @item pmon @var{command}
14207 @kindex pmon@r{, MIPS remote}
14208 @cindex send PMON command
14209 This command allows sending an arbitrary @var{command} string to the
14210 monitor. The monitor must be in debug mode for this to work.
14213 @node OpenRISC 1000
14214 @subsection OpenRISC 1000
14215 @cindex OpenRISC 1000
14217 @cindex or1k boards
14218 See OR1k Architecture document (@uref{www.opencores.org}) for more information
14219 about platform and commands.
14223 @kindex target jtag
14224 @item target jtag jtag://@var{host}:@var{port}
14226 Connects to remote JTAG server.
14227 JTAG remote server can be either an or1ksim or JTAG server,
14228 connected via parallel port to the board.
14230 Example: @code{target jtag jtag://localhost:9999}
14233 @item or1ksim @var{command}
14234 If connected to @code{or1ksim} OpenRISC 1000 Architectural
14235 Simulator, proprietary commands can be executed.
14237 @kindex info or1k spr
14238 @item info or1k spr
14239 Displays spr groups.
14241 @item info or1k spr @var{group}
14242 @itemx info or1k spr @var{groupno}
14243 Displays register names in selected group.
14245 @item info or1k spr @var{group} @var{register}
14246 @itemx info or1k spr @var{register}
14247 @itemx info or1k spr @var{groupno} @var{registerno}
14248 @itemx info or1k spr @var{registerno}
14249 Shows information about specified spr register.
14252 @item spr @var{group} @var{register} @var{value}
14253 @itemx spr @var{register @var{value}}
14254 @itemx spr @var{groupno} @var{registerno @var{value}}
14255 @itemx spr @var{registerno @var{value}}
14256 Writes @var{value} to specified spr register.
14259 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
14260 It is very similar to @value{GDBN} trace, except it does not interfere with normal
14261 program execution and is thus much faster. Hardware breakpoints/watchpoint
14262 triggers can be set using:
14265 Load effective address/data
14267 Store effective address/data
14269 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
14274 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
14275 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
14277 @code{htrace} commands:
14278 @cindex OpenRISC 1000 htrace
14281 @item hwatch @var{conditional}
14282 Set hardware watchpoint on combination of Load/Store Effecive Address(es)
14283 or Data. For example:
14285 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
14287 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
14291 Display information about current HW trace configuration.
14293 @item htrace trigger @var{conditional}
14294 Set starting criteria for HW trace.
14296 @item htrace qualifier @var{conditional}
14297 Set acquisition qualifier for HW trace.
14299 @item htrace stop @var{conditional}
14300 Set HW trace stopping criteria.
14302 @item htrace record [@var{data}]*
14303 Selects the data to be recorded, when qualifier is met and HW trace was
14306 @item htrace enable
14307 @itemx htrace disable
14308 Enables/disables the HW trace.
14310 @item htrace rewind [@var{filename}]
14311 Clears currently recorded trace data.
14313 If filename is specified, new trace file is made and any newly collected data
14314 will be written there.
14316 @item htrace print [@var{start} [@var{len}]]
14317 Prints trace buffer, using current record configuration.
14319 @item htrace mode continuous
14320 Set continuous trace mode.
14322 @item htrace mode suspend
14323 Set suspend trace mode.
14328 @subsection PowerPC
14331 @kindex target dink32
14332 @item target dink32 @var{dev}
14333 DINK32 ROM monitor.
14335 @kindex target ppcbug
14336 @item target ppcbug @var{dev}
14337 @kindex target ppcbug1
14338 @item target ppcbug1 @var{dev}
14339 PPCBUG ROM monitor for PowerPC.
14342 @item target sds @var{dev}
14343 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
14346 @cindex SDS protocol
14347 The following commands specifi to the SDS protocol are supported
14351 @item set sdstimeout @var{nsec}
14352 @kindex set sdstimeout
14353 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
14354 default is 2 seconds.
14356 @item show sdstimeout
14357 @kindex show sdstimeout
14358 Show the current value of the SDS timeout.
14360 @item sds @var{command}
14361 @kindex sds@r{, a command}
14362 Send the specified @var{command} string to the SDS monitor.
14367 @subsection HP PA Embedded
14371 @kindex target op50n
14372 @item target op50n @var{dev}
14373 OP50N monitor, running on an OKI HPPA board.
14375 @kindex target w89k
14376 @item target w89k @var{dev}
14377 W89K monitor, running on a Winbond HPPA board.
14382 @subsection Renesas SH
14386 @kindex target hms@r{, with Renesas SH}
14387 @item target hms @var{dev}
14388 A Renesas SH board attached via serial line to your host. Use special
14389 commands @code{device} and @code{speed} to control the serial line and
14390 the communications speed used.
14392 @kindex target e7000@r{, with Renesas SH}
14393 @item target e7000 @var{dev}
14394 E7000 emulator for Renesas SH.
14396 @kindex target sh3@r{, with SH}
14397 @kindex target sh3e@r{, with SH}
14398 @item target sh3 @var{dev}
14399 @item target sh3e @var{dev}
14400 Renesas SH-3 and SH-3E target systems.
14405 @subsection Tsqware Sparclet
14409 @value{GDBN} enables developers to debug tasks running on
14410 Sparclet targets from a Unix host.
14411 @value{GDBN} uses code that runs on
14412 both the Unix host and on the Sparclet target. The program
14413 @code{@value{GDBP}} is installed and executed on the Unix host.
14416 @item remotetimeout @var{args}
14417 @kindex remotetimeout
14418 @value{GDBN} supports the option @code{remotetimeout}.
14419 This option is set by the user, and @var{args} represents the number of
14420 seconds @value{GDBN} waits for responses.
14423 @cindex compiling, on Sparclet
14424 When compiling for debugging, include the options @samp{-g} to get debug
14425 information and @samp{-Ttext} to relocate the program to where you wish to
14426 load it on the target. You may also want to add the options @samp{-n} or
14427 @samp{-N} in order to reduce the size of the sections. Example:
14430 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
14433 You can use @code{objdump} to verify that the addresses are what you intended:
14436 sparclet-aout-objdump --headers --syms prog
14439 @cindex running, on Sparclet
14441 your Unix execution search path to find @value{GDBN}, you are ready to
14442 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
14443 (or @code{sparclet-aout-gdb}, depending on your installation).
14445 @value{GDBN} comes up showing the prompt:
14452 * Sparclet File:: Setting the file to debug
14453 * Sparclet Connection:: Connecting to Sparclet
14454 * Sparclet Download:: Sparclet download
14455 * Sparclet Execution:: Running and debugging
14458 @node Sparclet File
14459 @subsubsection Setting file to debug
14461 The @value{GDBN} command @code{file} lets you choose with program to debug.
14464 (gdbslet) file prog
14468 @value{GDBN} then attempts to read the symbol table of @file{prog}.
14469 @value{GDBN} locates
14470 the file by searching the directories listed in the command search
14472 If the file was compiled with debug information (option "-g"), source
14473 files will be searched as well.
14474 @value{GDBN} locates
14475 the source files by searching the directories listed in the directory search
14476 path (@pxref{Environment, ,Your program's environment}).
14478 to find a file, it displays a message such as:
14481 prog: No such file or directory.
14484 When this happens, add the appropriate directories to the search paths with
14485 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
14486 @code{target} command again.
14488 @node Sparclet Connection
14489 @subsubsection Connecting to Sparclet
14491 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
14492 To connect to a target on serial port ``@code{ttya}'', type:
14495 (gdbslet) target sparclet /dev/ttya
14496 Remote target sparclet connected to /dev/ttya
14497 main () at ../prog.c:3
14501 @value{GDBN} displays messages like these:
14507 @node Sparclet Download
14508 @subsubsection Sparclet download
14510 @cindex download to Sparclet
14511 Once connected to the Sparclet target,
14512 you can use the @value{GDBN}
14513 @code{load} command to download the file from the host to the target.
14514 The file name and load offset should be given as arguments to the @code{load}
14516 Since the file format is aout, the program must be loaded to the starting
14517 address. You can use @code{objdump} to find out what this value is. The load
14518 offset is an offset which is added to the VMA (virtual memory address)
14519 of each of the file's sections.
14520 For instance, if the program
14521 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
14522 and bss at 0x12010170, in @value{GDBN}, type:
14525 (gdbslet) load prog 0x12010000
14526 Loading section .text, size 0xdb0 vma 0x12010000
14529 If the code is loaded at a different address then what the program was linked
14530 to, you may need to use the @code{section} and @code{add-symbol-file} commands
14531 to tell @value{GDBN} where to map the symbol table.
14533 @node Sparclet Execution
14534 @subsubsection Running and debugging
14536 @cindex running and debugging Sparclet programs
14537 You can now begin debugging the task using @value{GDBN}'s execution control
14538 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
14539 manual for the list of commands.
14543 Breakpoint 1 at 0x12010000: file prog.c, line 3.
14545 Starting program: prog
14546 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
14547 3 char *symarg = 0;
14549 4 char *execarg = "hello!";
14554 @subsection Fujitsu Sparclite
14558 @kindex target sparclite
14559 @item target sparclite @var{dev}
14560 Fujitsu sparclite boards, used only for the purpose of loading.
14561 You must use an additional command to debug the program.
14562 For example: target remote @var{dev} using @value{GDBN} standard
14568 @subsection Tandem ST2000
14570 @value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's
14573 To connect your ST2000 to the host system, see the manufacturer's
14574 manual. Once the ST2000 is physically attached, you can run:
14577 target st2000 @var{dev} @var{speed}
14581 to establish it as your debugging environment. @var{dev} is normally
14582 the name of a serial device, such as @file{/dev/ttya}, connected to the
14583 ST2000 via a serial line. You can instead specify @var{dev} as a TCP
14584 connection (for example, to a serial line attached via a terminal
14585 concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}.
14587 The @code{load} and @code{attach} commands are @emph{not} defined for
14588 this target; you must load your program into the ST2000 as you normally
14589 would for standalone operation. @value{GDBN} reads debugging information
14590 (such as symbols) from a separate, debugging version of the program
14591 available on your host computer.
14592 @c FIXME!! This is terribly vague; what little content is here is
14593 @c basically hearsay.
14595 @cindex ST2000 auxiliary commands
14596 These auxiliary @value{GDBN} commands are available to help you with the ST2000
14600 @item st2000 @var{command}
14601 @kindex st2000 @var{cmd}
14602 @cindex STDBUG commands (ST2000)
14603 @cindex commands to STDBUG (ST2000)
14604 Send a @var{command} to the STDBUG monitor. See the manufacturer's
14605 manual for available commands.
14608 @cindex connect (to STDBUG)
14609 Connect the controlling terminal to the STDBUG command monitor. When
14610 you are done interacting with STDBUG, typing either of two character
14611 sequences gets you back to the @value{GDBN} command prompt:
14612 @kbd{@key{RET}~.} (Return, followed by tilde and period) or
14613 @kbd{@key{RET}~@key{C-d}} (Return, followed by tilde and control-D).
14617 @subsection Zilog Z8000
14620 @cindex simulator, Z8000
14621 @cindex Zilog Z8000 simulator
14623 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
14626 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
14627 unsegmented variant of the Z8000 architecture) or the Z8001 (the
14628 segmented variant). The simulator recognizes which architecture is
14629 appropriate by inspecting the object code.
14632 @item target sim @var{args}
14634 @kindex target sim@r{, with Z8000}
14635 Debug programs on a simulated CPU. If the simulator supports setup
14636 options, specify them via @var{args}.
14640 After specifying this target, you can debug programs for the simulated
14641 CPU in the same style as programs for your host computer; use the
14642 @code{file} command to load a new program image, the @code{run} command
14643 to run your program, and so on.
14645 As well as making available all the usual machine registers
14646 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
14647 additional items of information as specially named registers:
14652 Counts clock-ticks in the simulator.
14655 Counts instructions run in the simulator.
14658 Execution time in 60ths of a second.
14662 You can refer to these values in @value{GDBN} expressions with the usual
14663 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
14664 conditional breakpoint that suspends only after at least 5000
14665 simulated clock ticks.
14668 @subsection Atmel AVR
14671 When configured for debugging the Atmel AVR, @value{GDBN} supports the
14672 following AVR-specific commands:
14675 @item info io_registers
14676 @kindex info io_registers@r{, AVR}
14677 @cindex I/O registers (Atmel AVR)
14678 This command displays information about the AVR I/O registers. For
14679 each register, @value{GDBN} prints its number and value.
14686 When configured for debugging CRIS, @value{GDBN} provides the
14687 following CRIS-specific commands:
14690 @item set cris-version @var{ver}
14691 @cindex CRIS version
14692 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
14693 The CRIS version affects register names and sizes. This command is useful in
14694 case autodetection of the CRIS version fails.
14696 @item show cris-version
14697 Show the current CRIS version.
14699 @item set cris-dwarf2-cfi
14700 @cindex DWARF-2 CFI and CRIS
14701 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
14702 Change to @samp{off} when using @code{gcc-cris} whose version is below
14705 @item show cris-dwarf2-cfi
14706 Show the current state of using DWARF-2 CFI.
14708 @item set cris-mode @var{mode}
14710 Set the current CRIS mode to @var{mode}. It should only be changed when
14711 debugging in guru mode, in which case it should be set to
14712 @samp{guru} (the default is @samp{normal}).
14714 @item show cris-mode
14715 Show the current CRIS mode.
14719 @subsection Renesas Super-H
14722 For the Renesas Super-H processor, @value{GDBN} provides these
14727 @kindex regs@r{, Super-H}
14728 Show the values of all Super-H registers.
14732 @subsection Windows CE
14735 The following commands are available for Windows CE:
14738 @item set remotedirectory @var{dir}
14739 @kindex set remotedirectory
14740 Tell @value{GDBN} to upload files from the named directory @var{dir}.
14741 The default is @file{/gdb}, i.e.@: the root directory on the current
14744 @item show remotedirectory
14745 @kindex show remotedirectory
14746 Show the current value of the upload directory.
14748 @item set remoteupload @var{method}
14749 @kindex set remoteupload
14750 Set the method used to upload files to remote device. Valid values
14751 for @var{method} are @samp{always}, @samp{newer}, and @samp{never}.
14752 The default is @samp{newer}.
14754 @item show remoteupload
14755 @kindex show remoteupload
14756 Show the current setting of the upload method.
14758 @item set remoteaddhost
14759 @kindex set remoteaddhost
14760 Tell @value{GDBN} whether to add this host to the remote stub's
14761 arguments when you debug over a network.
14763 @item show remoteaddhost
14764 @kindex show remoteaddhost
14765 Show whether to add this host to remote stub's arguments when
14766 debugging over a network.
14770 @node Architectures
14771 @section Architectures
14773 This section describes characteristics of architectures that affect
14774 all uses of @value{GDBN} with the architecture, both native and cross.
14781 * HPPA:: HP PA architecture
14785 @subsection x86 Architecture-specific issues.
14788 @item set struct-convention @var{mode}
14789 @kindex set struct-convention
14790 @cindex struct return convention
14791 @cindex struct/union returned in registers
14792 Set the convention used by the inferior to return @code{struct}s and
14793 @code{union}s from functions to @var{mode}. Possible values of
14794 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
14795 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
14796 are returned on the stack, while @code{"reg"} means that a
14797 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
14798 be returned in a register.
14800 @item show struct-convention
14801 @kindex show struct-convention
14802 Show the current setting of the convention to return @code{struct}s
14811 @kindex set rstack_high_address
14812 @cindex AMD 29K register stack
14813 @cindex register stack, AMD29K
14814 @item set rstack_high_address @var{address}
14815 On AMD 29000 family processors, registers are saved in a separate
14816 @dfn{register stack}. There is no way for @value{GDBN} to determine the
14817 extent of this stack. Normally, @value{GDBN} just assumes that the
14818 stack is ``large enough''. This may result in @value{GDBN} referencing
14819 memory locations that do not exist. If necessary, you can get around
14820 this problem by specifying the ending address of the register stack with
14821 the @code{set rstack_high_address} command. The argument should be an
14822 address, which you probably want to precede with @samp{0x} to specify in
14825 @kindex show rstack_high_address
14826 @item show rstack_high_address
14827 Display the current limit of the register stack, on AMD 29000 family
14835 See the following section.
14840 @cindex stack on Alpha
14841 @cindex stack on MIPS
14842 @cindex Alpha stack
14844 Alpha- and MIPS-based computers use an unusual stack frame, which
14845 sometimes requires @value{GDBN} to search backward in the object code to
14846 find the beginning of a function.
14848 @cindex response time, MIPS debugging
14849 To improve response time (especially for embedded applications, where
14850 @value{GDBN} may be restricted to a slow serial line for this search)
14851 you may want to limit the size of this search, using one of these
14855 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
14856 @item set heuristic-fence-post @var{limit}
14857 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
14858 search for the beginning of a function. A value of @var{0} (the
14859 default) means there is no limit. However, except for @var{0}, the
14860 larger the limit the more bytes @code{heuristic-fence-post} must search
14861 and therefore the longer it takes to run. You should only need to use
14862 this command when debugging a stripped executable.
14864 @item show heuristic-fence-post
14865 Display the current limit.
14869 These commands are available @emph{only} when @value{GDBN} is configured
14870 for debugging programs on Alpha or MIPS processors.
14872 Several MIPS-specific commands are available when debugging MIPS
14876 @item set mips saved-gpreg-size @var{size}
14877 @kindex set mips saved-gpreg-size
14878 @cindex MIPS GP register size on stack
14879 Set the size of MIPS general-purpose registers saved on the stack.
14880 The argument @var{size} can be one of the following:
14884 32-bit GP registers
14886 64-bit GP registers
14888 Use the target's default setting or autodetect the saved size from the
14889 information contained in the executable. This is the default
14892 @item show mips saved-gpreg-size
14893 @kindex show mips saved-gpreg-size
14894 Show the current size of MIPS GP registers on the stack.
14896 @item set mips stack-arg-size @var{size}
14897 @kindex set mips stack-arg-size
14898 @cindex MIPS stack space for arguments
14899 Set the amount of stack space reserved for arguments to functions.
14900 The argument can be one of @code{"32"}, @code{"64"} or @code{"auto"}
14903 @item set mips abi @var{arg}
14904 @kindex set mips abi
14905 @cindex set ABI for MIPS
14906 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
14907 values of @var{arg} are:
14911 The default ABI associated with the current binary (this is the
14922 @item show mips abi
14923 @kindex show mips abi
14924 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
14927 @itemx show mipsfpu
14928 @xref{MIPS Embedded, set mipsfpu}.
14930 @item set mips mask-address @var{arg}
14931 @kindex set mips mask-address
14932 @cindex MIPS addresses, masking
14933 This command determines whether the most-significant 32 bits of 64-bit
14934 MIPS addresses are masked off. The argument @var{arg} can be
14935 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
14936 setting, which lets @value{GDBN} determine the correct value.
14938 @item show mips mask-address
14939 @kindex show mips mask-address
14940 Show whether the upper 32 bits of MIPS addresses are masked off or
14943 @item set remote-mips64-transfers-32bit-regs
14944 @kindex set remote-mips64-transfers-32bit-regs
14945 This command controls compatibility with 64-bit MIPS targets that
14946 transfer data in 32-bit quantities. If you have an old MIPS 64 target
14947 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
14948 and 64 bits for other registers, set this option to @samp{on}.
14950 @item show remote-mips64-transfers-32bit-regs
14951 @kindex show remote-mips64-transfers-32bit-regs
14952 Show the current setting of compatibility with older MIPS 64 targets.
14954 @item set debug mips
14955 @kindex set debug mips
14956 This command turns on and off debugging messages for the MIPS-specific
14957 target code in @value{GDBN}.
14959 @item show debug mips
14960 @kindex show debug mips
14961 Show the current setting of MIPS debugging messages.
14967 @cindex HPPA support
14969 When @value{GDBN} is debugging te HP PA architecture, it provides the
14970 following special commands:
14973 @item set debug hppa
14974 @kindex set debug hppa
14975 THis command determines whether HPPA architecture specific debugging
14976 messages are to be displayed.
14978 @item show debug hppa
14979 Show whether HPPA debugging messages are displayed.
14981 @item maint print unwind @var{address}
14982 @kindex maint print unwind@r{, HPPA}
14983 This command displays the contents of the unwind table entry at the
14984 given @var{address}.
14989 @node Controlling GDB
14990 @chapter Controlling @value{GDBN}
14992 You can alter the way @value{GDBN} interacts with you by using the
14993 @code{set} command. For commands controlling how @value{GDBN} displays
14994 data, see @ref{Print Settings, ,Print settings}. Other settings are
14999 * Editing:: Command editing
15000 * History:: Command history
15001 * Screen Size:: Screen size
15002 * Numbers:: Numbers
15003 * ABI:: Configuring the current ABI
15004 * Messages/Warnings:: Optional warnings and messages
15005 * Debugging Output:: Optional messages about internal happenings
15013 @value{GDBN} indicates its readiness to read a command by printing a string
15014 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
15015 can change the prompt string with the @code{set prompt} command. For
15016 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
15017 the prompt in one of the @value{GDBN} sessions so that you can always tell
15018 which one you are talking to.
15020 @emph{Note:} @code{set prompt} does not add a space for you after the
15021 prompt you set. This allows you to set a prompt which ends in a space
15022 or a prompt that does not.
15026 @item set prompt @var{newprompt}
15027 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
15029 @kindex show prompt
15031 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
15035 @section Command editing
15037 @cindex command line editing
15039 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
15040 @sc{gnu} library provides consistent behavior for programs which provide a
15041 command line interface to the user. Advantages are @sc{gnu} Emacs-style
15042 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
15043 substitution, and a storage and recall of command history across
15044 debugging sessions.
15046 You may control the behavior of command line editing in @value{GDBN} with the
15047 command @code{set}.
15050 @kindex set editing
15053 @itemx set editing on
15054 Enable command line editing (enabled by default).
15056 @item set editing off
15057 Disable command line editing.
15059 @kindex show editing
15061 Show whether command line editing is enabled.
15064 @xref{Command Line Editing}, for more details about the Readline
15065 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
15066 encouraged to read that chapter.
15069 @section Command history
15070 @cindex command history
15072 @value{GDBN} can keep track of the commands you type during your
15073 debugging sessions, so that you can be certain of precisely what
15074 happened. Use these commands to manage the @value{GDBN} command
15077 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
15078 package, to provide the history facility. @xref{Using History
15079 Interactively}, for the detailed description of the History library.
15081 Here is the description of @value{GDBN} commands related to command
15085 @cindex history substitution
15086 @cindex history file
15087 @kindex set history filename
15088 @cindex @env{GDBHISTFILE}, environment variable
15089 @item set history filename @var{fname}
15090 Set the name of the @value{GDBN} command history file to @var{fname}.
15091 This is the file where @value{GDBN} reads an initial command history
15092 list, and where it writes the command history from this session when it
15093 exits. You can access this list through history expansion or through
15094 the history command editing characters listed below. This file defaults
15095 to the value of the environment variable @code{GDBHISTFILE}, or to
15096 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
15099 @cindex save command history
15100 @kindex set history save
15101 @item set history save
15102 @itemx set history save on
15103 Record command history in a file, whose name may be specified with the
15104 @code{set history filename} command. By default, this option is disabled.
15106 @item set history save off
15107 Stop recording command history in a file.
15109 @cindex history size
15110 @kindex set history size
15111 @cindex @env{HISTSIZE}, environment variable
15112 @item set history size @var{size}
15113 Set the number of commands which @value{GDBN} keeps in its history list.
15114 This defaults to the value of the environment variable
15115 @code{HISTSIZE}, or to 256 if this variable is not set.
15118 History expansion assigns special meaning to the character @kbd{!}.
15119 @xref{Event Designators}, for more details.
15121 @cindex history expansion, turn on/off
15122 Since @kbd{!} is also the logical not operator in C, history expansion
15123 is off by default. If you decide to enable history expansion with the
15124 @code{set history expansion on} command, you may sometimes need to
15125 follow @kbd{!} (when it is used as logical not, in an expression) with
15126 a space or a tab to prevent it from being expanded. The readline
15127 history facilities do not attempt substitution on the strings
15128 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
15130 The commands to control history expansion are:
15133 @item set history expansion on
15134 @itemx set history expansion
15135 @kindex set history expansion
15136 Enable history expansion. History expansion is off by default.
15138 @item set history expansion off
15139 Disable history expansion.
15142 @kindex show history
15144 @itemx show history filename
15145 @itemx show history save
15146 @itemx show history size
15147 @itemx show history expansion
15148 These commands display the state of the @value{GDBN} history parameters.
15149 @code{show history} by itself displays all four states.
15154 @kindex show commands
15155 @cindex show last commands
15156 @cindex display command history
15157 @item show commands
15158 Display the last ten commands in the command history.
15160 @item show commands @var{n}
15161 Print ten commands centered on command number @var{n}.
15163 @item show commands +
15164 Print ten commands just after the commands last printed.
15168 @section Screen size
15169 @cindex size of screen
15170 @cindex pauses in output
15172 Certain commands to @value{GDBN} may produce large amounts of
15173 information output to the screen. To help you read all of it,
15174 @value{GDBN} pauses and asks you for input at the end of each page of
15175 output. Type @key{RET} when you want to continue the output, or @kbd{q}
15176 to discard the remaining output. Also, the screen width setting
15177 determines when to wrap lines of output. Depending on what is being
15178 printed, @value{GDBN} tries to break the line at a readable place,
15179 rather than simply letting it overflow onto the following line.
15181 Normally @value{GDBN} knows the size of the screen from the terminal
15182 driver software. For example, on Unix @value{GDBN} uses the termcap data base
15183 together with the value of the @code{TERM} environment variable and the
15184 @code{stty rows} and @code{stty cols} settings. If this is not correct,
15185 you can override it with the @code{set height} and @code{set
15192 @kindex show height
15193 @item set height @var{lpp}
15195 @itemx set width @var{cpl}
15197 These @code{set} commands specify a screen height of @var{lpp} lines and
15198 a screen width of @var{cpl} characters. The associated @code{show}
15199 commands display the current settings.
15201 If you specify a height of zero lines, @value{GDBN} does not pause during
15202 output no matter how long the output is. This is useful if output is to a
15203 file or to an editor buffer.
15205 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
15206 from wrapping its output.
15208 @item set pagination on
15209 @itemx set pagination off
15210 @kindex set pagination
15211 Turn the output pagination on or off; the default is on. Turning
15212 pagination off is the alternative to @code{set height 0}.
15214 @item show pagination
15215 @kindex show pagination
15216 Show the current pagination mode.
15221 @cindex number representation
15222 @cindex entering numbers
15224 You can always enter numbers in octal, decimal, or hexadecimal in
15225 @value{GDBN} by the usual conventions: octal numbers begin with
15226 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
15227 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
15228 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
15229 10; likewise, the default display for numbers---when no particular
15230 format is specified---is base 10. You can change the default base for
15231 both input and output with the commands described below.
15234 @kindex set input-radix
15235 @item set input-radix @var{base}
15236 Set the default base for numeric input. Supported choices
15237 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15238 specified either unambiguously or using the current input radix; for
15242 set input-radix 012
15243 set input-radix 10.
15244 set input-radix 0xa
15248 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
15249 leaves the input radix unchanged, no matter what it was, since
15250 @samp{10}, being without any leading or trailing signs of its base, is
15251 interpreted in the current radix. Thus, if the current radix is 16,
15252 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
15255 @kindex set output-radix
15256 @item set output-radix @var{base}
15257 Set the default base for numeric display. Supported choices
15258 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15259 specified either unambiguously or using the current input radix.
15261 @kindex show input-radix
15262 @item show input-radix
15263 Display the current default base for numeric input.
15265 @kindex show output-radix
15266 @item show output-radix
15267 Display the current default base for numeric display.
15269 @item set radix @r{[}@var{base}@r{]}
15273 These commands set and show the default base for both input and output
15274 of numbers. @code{set radix} sets the radix of input and output to
15275 the same base; without an argument, it resets the radix back to its
15276 default value of 10.
15281 @section Configuring the current ABI
15283 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
15284 application automatically. However, sometimes you need to override its
15285 conclusions. Use these commands to manage @value{GDBN}'s view of the
15292 One @value{GDBN} configuration can debug binaries for multiple operating
15293 system targets, either via remote debugging or native emulation.
15294 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
15295 but you can override its conclusion using the @code{set osabi} command.
15296 One example where this is useful is in debugging of binaries which use
15297 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
15298 not have the same identifying marks that the standard C library for your
15303 Show the OS ABI currently in use.
15306 With no argument, show the list of registered available OS ABI's.
15308 @item set osabi @var{abi}
15309 Set the current OS ABI to @var{abi}.
15312 @cindex float promotion
15314 Generally, the way that an argument of type @code{float} is passed to a
15315 function depends on whether the function is prototyped. For a prototyped
15316 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
15317 according to the architecture's convention for @code{float}. For unprototyped
15318 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
15319 @code{double} and then passed.
15321 Unfortunately, some forms of debug information do not reliably indicate whether
15322 a function is prototyped. If @value{GDBN} calls a function that is not marked
15323 as prototyped, it consults @kbd{set coerce-float-to-double}.
15326 @kindex set coerce-float-to-double
15327 @item set coerce-float-to-double
15328 @itemx set coerce-float-to-double on
15329 Arguments of type @code{float} will be promoted to @code{double} when passed
15330 to an unprototyped function. This is the default setting.
15332 @item set coerce-float-to-double off
15333 Arguments of type @code{float} will be passed directly to unprototyped
15336 @kindex show coerce-float-to-double
15337 @item show coerce-float-to-double
15338 Show the current setting of promoting @code{float} to @code{double}.
15342 @kindex show cp-abi
15343 @value{GDBN} needs to know the ABI used for your program's C@t{++}
15344 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
15345 used to build your application. @value{GDBN} only fully supports
15346 programs with a single C@t{++} ABI; if your program contains code using
15347 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
15348 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
15349 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
15350 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
15351 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
15352 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
15357 Show the C@t{++} ABI currently in use.
15360 With no argument, show the list of supported C@t{++} ABI's.
15362 @item set cp-abi @var{abi}
15363 @itemx set cp-abi auto
15364 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
15367 @node Messages/Warnings
15368 @section Optional warnings and messages
15370 @cindex verbose operation
15371 @cindex optional warnings
15372 By default, @value{GDBN} is silent about its inner workings. If you are
15373 running on a slow machine, you may want to use the @code{set verbose}
15374 command. This makes @value{GDBN} tell you when it does a lengthy
15375 internal operation, so you will not think it has crashed.
15377 Currently, the messages controlled by @code{set verbose} are those
15378 which announce that the symbol table for a source file is being read;
15379 see @code{symbol-file} in @ref{Files, ,Commands to specify files}.
15382 @kindex set verbose
15383 @item set verbose on
15384 Enables @value{GDBN} output of certain informational messages.
15386 @item set verbose off
15387 Disables @value{GDBN} output of certain informational messages.
15389 @kindex show verbose
15391 Displays whether @code{set verbose} is on or off.
15394 By default, if @value{GDBN} encounters bugs in the symbol table of an
15395 object file, it is silent; but if you are debugging a compiler, you may
15396 find this information useful (@pxref{Symbol Errors, ,Errors reading
15401 @kindex set complaints
15402 @item set complaints @var{limit}
15403 Permits @value{GDBN} to output @var{limit} complaints about each type of
15404 unusual symbols before becoming silent about the problem. Set
15405 @var{limit} to zero to suppress all complaints; set it to a large number
15406 to prevent complaints from being suppressed.
15408 @kindex show complaints
15409 @item show complaints
15410 Displays how many symbol complaints @value{GDBN} is permitted to produce.
15414 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
15415 lot of stupid questions to confirm certain commands. For example, if
15416 you try to run a program which is already running:
15420 The program being debugged has been started already.
15421 Start it from the beginning? (y or n)
15424 If you are willing to unflinchingly face the consequences of your own
15425 commands, you can disable this ``feature'':
15429 @kindex set confirm
15431 @cindex confirmation
15432 @cindex stupid questions
15433 @item set confirm off
15434 Disables confirmation requests.
15436 @item set confirm on
15437 Enables confirmation requests (the default).
15439 @kindex show confirm
15441 Displays state of confirmation requests.
15445 @node Debugging Output
15446 @section Optional messages about internal happenings
15447 @cindex optional debugging messages
15449 @value{GDBN} has commands that enable optional debugging messages from
15450 various @value{GDBN} subsystems; normally these commands are of
15451 interest to @value{GDBN} maintainers, or when reporting a bug. This
15452 section documents those commands.
15455 @kindex set exec-done-display
15456 @item set exec-done-display
15457 Turns on or off the notification of asynchronous commands'
15458 completion. When on, @value{GDBN} will print a message when an
15459 asynchronous command finishes its execution. The default is off.
15460 @kindex show exec-done-display
15461 @item show exec-done-display
15462 Displays the current setting of asynchronous command completion
15465 @cindex gdbarch debugging info
15466 @cindex architecture debugging info
15467 @item set debug arch
15468 Turns on or off display of gdbarch debugging info. The default is off
15470 @item show debug arch
15471 Displays the current state of displaying gdbarch debugging info.
15472 @item set debug aix-thread
15473 @cindex AIX threads
15474 Display debugging messages about inner workings of the AIX thread
15476 @item show debug aix-thread
15477 Show the current state of AIX thread debugging info display.
15478 @item set debug event
15479 @cindex event debugging info
15480 Turns on or off display of @value{GDBN} event debugging info. The
15482 @item show debug event
15483 Displays the current state of displaying @value{GDBN} event debugging
15485 @item set debug expression
15486 @cindex expression debugging info
15487 Turns on or off display of debugging info about @value{GDBN}
15488 expression parsing. The default is off.
15489 @item show debug expression
15490 Displays the current state of displaying debugging info about
15491 @value{GDBN} expression parsing.
15492 @item set debug frame
15493 @cindex frame debugging info
15494 Turns on or off display of @value{GDBN} frame debugging info. The
15496 @item show debug frame
15497 Displays the current state of displaying @value{GDBN} frame debugging
15499 @item set debug infrun
15500 @cindex inferior debugging info
15501 Turns on or off display of @value{GDBN} debugging info for running the inferior.
15502 The default is off. @file{infrun.c} contains GDB's runtime state machine used
15503 for implementing operations such as single-stepping the inferior.
15504 @item show debug infrun
15505 Displays the current state of @value{GDBN} inferior debugging.
15506 @item set debug lin-lwp
15507 @cindex @sc{gnu}/Linux LWP debug messages
15508 @cindex Linux lightweight processes
15509 Turns on or off debugging messages from the Linux LWP debug support.
15510 @item show debug lin-lwp
15511 Show the current state of Linux LWP debugging messages.
15512 @item set debug observer
15513 @cindex observer debugging info
15514 Turns on or off display of @value{GDBN} observer debugging. This
15515 includes info such as the notification of observable events.
15516 @item show debug observer
15517 Displays the current state of observer debugging.
15518 @item set debug overload
15519 @cindex C@t{++} overload debugging info
15520 Turns on or off display of @value{GDBN} C@t{++} overload debugging
15521 info. This includes info such as ranking of functions, etc. The default
15523 @item show debug overload
15524 Displays the current state of displaying @value{GDBN} C@t{++} overload
15526 @cindex packets, reporting on stdout
15527 @cindex serial connections, debugging
15528 @item set debug remote
15529 Turns on or off display of reports on all packets sent back and forth across
15530 the serial line to the remote machine. The info is printed on the
15531 @value{GDBN} standard output stream. The default is off.
15532 @item show debug remote
15533 Displays the state of display of remote packets.
15534 @item set debug serial
15535 Turns on or off display of @value{GDBN} serial debugging info. The
15537 @item show debug serial
15538 Displays the current state of displaying @value{GDBN} serial debugging
15540 @item set debug solib-frv
15541 @cindex FR-V shared-library debugging
15542 Turns on or off debugging messages for FR-V shared-library code.
15543 @item show debug solib-frv
15544 Display the current state of FR-V shared-library code debugging
15546 @item set debug target
15547 @cindex target debugging info
15548 Turns on or off display of @value{GDBN} target debugging info. This info
15549 includes what is going on at the target level of GDB, as it happens. The
15550 default is 0. Set it to 1 to track events, and to 2 to also track the
15551 value of large memory transfers. Changes to this flag do not take effect
15552 until the next time you connect to a target or use the @code{run} command.
15553 @item show debug target
15554 Displays the current state of displaying @value{GDBN} target debugging
15556 @item set debugvarobj
15557 @cindex variable object debugging info
15558 Turns on or off display of @value{GDBN} variable object debugging
15559 info. The default is off.
15560 @item show debugvarobj
15561 Displays the current state of displaying @value{GDBN} variable object
15566 @chapter Canned Sequences of Commands
15568 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
15569 command lists}), @value{GDBN} provides two ways to store sequences of
15570 commands for execution as a unit: user-defined commands and command
15574 * Define:: User-defined commands
15575 * Hooks:: User-defined command hooks
15576 * Command Files:: Command files
15577 * Output:: Commands for controlled output
15581 @section User-defined commands
15583 @cindex user-defined command
15584 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
15585 which you assign a new name as a command. This is done with the
15586 @code{define} command. User commands may accept up to 10 arguments
15587 separated by whitespace. Arguments are accessed within the user command
15588 via @var{$arg0@dots{}$arg9}. A trivial example:
15592 print $arg0 + $arg1 + $arg2
15596 To execute the command use:
15603 This defines the command @code{adder}, which prints the sum of
15604 its three arguments. Note the arguments are text substitutions, so they may
15605 reference variables, use complex expressions, or even perform inferior
15611 @item define @var{commandname}
15612 Define a command named @var{commandname}. If there is already a command
15613 by that name, you are asked to confirm that you want to redefine it.
15615 The definition of the command is made up of other @value{GDBN} command lines,
15616 which are given following the @code{define} command. The end of these
15617 commands is marked by a line containing @code{end}.
15623 Takes a single argument, which is an expression to evaluate.
15624 It is followed by a series of commands that are executed
15625 only if the expression is true (nonzero).
15626 There can then optionally be a line @code{else}, followed
15627 by a series of commands that are only executed if the expression
15628 was false. The end of the list is marked by a line containing @code{end}.
15632 The syntax is similar to @code{if}: the command takes a single argument,
15633 which is an expression to evaluate, and must be followed by the commands to
15634 execute, one per line, terminated by an @code{end}.
15635 The commands are executed repeatedly as long as the expression
15639 @item document @var{commandname}
15640 Document the user-defined command @var{commandname}, so that it can be
15641 accessed by @code{help}. The command @var{commandname} must already be
15642 defined. This command reads lines of documentation just as @code{define}
15643 reads the lines of the command definition, ending with @code{end}.
15644 After the @code{document} command is finished, @code{help} on command
15645 @var{commandname} displays the documentation you have written.
15647 You may use the @code{document} command again to change the
15648 documentation of a command. Redefining the command with @code{define}
15649 does not change the documentation.
15651 @kindex dont-repeat
15652 @cindex don't repeat command
15654 Used inside a user-defined command, this tells @value{GDBN} that this
15655 command should not be repeated when the user hits @key{RET}
15656 (@pxref{Command Syntax, repeat last command}).
15658 @kindex help user-defined
15659 @item help user-defined
15660 List all user-defined commands, with the first line of the documentation
15665 @itemx show user @var{commandname}
15666 Display the @value{GDBN} commands used to define @var{commandname} (but
15667 not its documentation). If no @var{commandname} is given, display the
15668 definitions for all user-defined commands.
15670 @cindex infinite recusrion in user-defined commands
15671 @kindex show max-user-call-depth
15672 @kindex set max-user-call-depth
15673 @item show max-user-call-depth
15674 @itemx set max-user-call-depth
15675 The value of @code{max-user-call-depth} controls how many recursion
15676 levels are allowed in user-defined commands before GDB suspects an
15677 infinite recursion and aborts the command.
15681 When user-defined commands are executed, the
15682 commands of the definition are not printed. An error in any command
15683 stops execution of the user-defined command.
15685 If used interactively, commands that would ask for confirmation proceed
15686 without asking when used inside a user-defined command. Many @value{GDBN}
15687 commands that normally print messages to say what they are doing omit the
15688 messages when used in a user-defined command.
15691 @section User-defined command hooks
15692 @cindex command hooks
15693 @cindex hooks, for commands
15694 @cindex hooks, pre-command
15697 You may define @dfn{hooks}, which are a special kind of user-defined
15698 command. Whenever you run the command @samp{foo}, if the user-defined
15699 command @samp{hook-foo} exists, it is executed (with no arguments)
15700 before that command.
15702 @cindex hooks, post-command
15704 A hook may also be defined which is run after the command you executed.
15705 Whenever you run the command @samp{foo}, if the user-defined command
15706 @samp{hookpost-foo} exists, it is executed (with no arguments) after
15707 that command. Post-execution hooks may exist simultaneously with
15708 pre-execution hooks, for the same command.
15710 It is valid for a hook to call the command which it hooks. If this
15711 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
15713 @c It would be nice if hookpost could be passed a parameter indicating
15714 @c if the command it hooks executed properly or not. FIXME!
15716 @kindex stop@r{, a pseudo-command}
15717 In addition, a pseudo-command, @samp{stop} exists. Defining
15718 (@samp{hook-stop}) makes the associated commands execute every time
15719 execution stops in your program: before breakpoint commands are run,
15720 displays are printed, or the stack frame is printed.
15722 For example, to ignore @code{SIGALRM} signals while
15723 single-stepping, but treat them normally during normal execution,
15728 handle SIGALRM nopass
15732 handle SIGALRM pass
15735 define hook-continue
15736 handle SIGLARM pass
15740 As a further example, to hook at the begining and end of the @code{echo}
15741 command, and to add extra text to the beginning and end of the message,
15749 define hookpost-echo
15753 (@value{GDBP}) echo Hello World
15754 <<<---Hello World--->>>
15759 You can define a hook for any single-word command in @value{GDBN}, but
15760 not for command aliases; you should define a hook for the basic command
15761 name, e.g. @code{backtrace} rather than @code{bt}.
15762 @c FIXME! So how does Joe User discover whether a command is an alias
15764 If an error occurs during the execution of your hook, execution of
15765 @value{GDBN} commands stops and @value{GDBN} issues a prompt
15766 (before the command that you actually typed had a chance to run).
15768 If you try to define a hook which does not match any known command, you
15769 get a warning from the @code{define} command.
15771 @node Command Files
15772 @section Command files
15774 @cindex command files
15775 A command file for @value{GDBN} is a text file made of lines that are
15776 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
15777 also be included. An empty line in a command file does nothing; it
15778 does not mean to repeat the last command, as it would from the
15781 You can request the execution of a command file with the @code{source}
15786 @item source @var{filename}
15787 Execute the command file @var{filename}.
15790 The lines in a command file are executed sequentially. They are not
15791 printed as they are executed. An error in any command terminates
15792 execution of the command file and control is returned to the console.
15794 Commands that would ask for confirmation if used interactively proceed
15795 without asking when used in a command file. Many @value{GDBN} commands that
15796 normally print messages to say what they are doing omit the messages
15797 when called from command files.
15799 @value{GDBN} also accepts command input from standard input. In this
15800 mode, normal output goes to standard output and error output goes to
15801 standard error. Errors in a command file supplied on standard input do
15802 not terminate execution of the command file---execution continues with
15806 gdb < cmds > log 2>&1
15809 (The syntax above will vary depending on the shell used.) This example
15810 will execute commands from the file @file{cmds}. All output and errors
15811 would be directed to @file{log}.
15814 @section Commands for controlled output
15816 During the execution of a command file or a user-defined command, normal
15817 @value{GDBN} output is suppressed; the only output that appears is what is
15818 explicitly printed by the commands in the definition. This section
15819 describes three commands useful for generating exactly the output you
15824 @item echo @var{text}
15825 @c I do not consider backslash-space a standard C escape sequence
15826 @c because it is not in ANSI.
15827 Print @var{text}. Nonprinting characters can be included in
15828 @var{text} using C escape sequences, such as @samp{\n} to print a
15829 newline. @strong{No newline is printed unless you specify one.}
15830 In addition to the standard C escape sequences, a backslash followed
15831 by a space stands for a space. This is useful for displaying a
15832 string with spaces at the beginning or the end, since leading and
15833 trailing spaces are otherwise trimmed from all arguments.
15834 To print @samp{@w{ }and foo =@w{ }}, use the command
15835 @samp{echo \@w{ }and foo = \@w{ }}.
15837 A backslash at the end of @var{text} can be used, as in C, to continue
15838 the command onto subsequent lines. For example,
15841 echo This is some text\n\
15842 which is continued\n\
15843 onto several lines.\n
15846 produces the same output as
15849 echo This is some text\n
15850 echo which is continued\n
15851 echo onto several lines.\n
15855 @item output @var{expression}
15856 Print the value of @var{expression} and nothing but that value: no
15857 newlines, no @samp{$@var{nn} = }. The value is not entered in the
15858 value history either. @xref{Expressions, ,Expressions}, for more information
15861 @item output/@var{fmt} @var{expression}
15862 Print the value of @var{expression} in format @var{fmt}. You can use
15863 the same formats as for @code{print}. @xref{Output Formats,,Output
15864 formats}, for more information.
15867 @item printf @var{string}, @var{expressions}@dots{}
15868 Print the values of the @var{expressions} under the control of
15869 @var{string}. The @var{expressions} are separated by commas and may be
15870 either numbers or pointers. Their values are printed as specified by
15871 @var{string}, exactly as if your program were to execute the C
15873 @c FIXME: the above implies that at least all ANSI C formats are
15874 @c supported, but it isn't true: %E and %G don't work (or so it seems).
15875 @c Either this is a bug, or the manual should document what formats are
15879 printf (@var{string}, @var{expressions}@dots{});
15882 For example, you can print two values in hex like this:
15885 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
15888 The only backslash-escape sequences that you can use in the format
15889 string are the simple ones that consist of backslash followed by a
15894 @chapter Command Interpreters
15895 @cindex command interpreters
15897 @value{GDBN} supports multiple command interpreters, and some command
15898 infrastructure to allow users or user interface writers to switch
15899 between interpreters or run commands in other interpreters.
15901 @value{GDBN} currently supports two command interpreters, the console
15902 interpreter (sometimes called the command-line interpreter or @sc{cli})
15903 and the machine interface interpreter (or @sc{gdb/mi}). This manual
15904 describes both of these interfaces in great detail.
15906 By default, @value{GDBN} will start with the console interpreter.
15907 However, the user may choose to start @value{GDBN} with another
15908 interpreter by specifying the @option{-i} or @option{--interpreter}
15909 startup options. Defined interpreters include:
15913 @cindex console interpreter
15914 The traditional console or command-line interpreter. This is the most often
15915 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
15916 @value{GDBN} will use this interpreter.
15919 @cindex mi interpreter
15920 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
15921 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
15922 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
15926 @cindex mi2 interpreter
15927 The current @sc{gdb/mi} interface.
15930 @cindex mi1 interpreter
15931 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
15935 @cindex invoke another interpreter
15936 The interpreter being used by @value{GDBN} may not be dynamically
15937 switched at runtime. Although possible, this could lead to a very
15938 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
15939 enters the command "interpreter-set console" in a console view,
15940 @value{GDBN} would switch to using the console interpreter, rendering
15941 the IDE inoperable!
15943 @kindex interpreter-exec
15944 Although you may only choose a single interpreter at startup, you may execute
15945 commands in any interpreter from the current interpreter using the appropriate
15946 command. If you are running the console interpreter, simply use the
15947 @code{interpreter-exec} command:
15950 interpreter-exec mi "-data-list-register-names"
15953 @sc{gdb/mi} has a similar command, although it is only available in versions of
15954 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
15957 @chapter @value{GDBN} Text User Interface
15959 @cindex Text User Interface
15962 * TUI Overview:: TUI overview
15963 * TUI Keys:: TUI key bindings
15964 * TUI Single Key Mode:: TUI single key mode
15965 * TUI Commands:: TUI specific commands
15966 * TUI Configuration:: TUI configuration variables
15969 The @value{GDBN} Text User Interface, TUI in short, is a terminal
15970 interface which uses the @code{curses} library to show the source
15971 file, the assembly output, the program registers and @value{GDBN}
15972 commands in separate text windows.
15974 The TUI is enabled by invoking @value{GDBN} using either
15976 @samp{gdbtui} or @samp{gdb -tui}.
15979 @section TUI overview
15981 The TUI has two display modes that can be switched while
15986 A curses (or TUI) mode in which it displays several text
15987 windows on the terminal.
15990 A standard mode which corresponds to the @value{GDBN} configured without
15994 In the TUI mode, @value{GDBN} can display several text window
15999 This window is the @value{GDBN} command window with the @value{GDBN}
16000 prompt and the @value{GDBN} outputs. The @value{GDBN} input is still
16001 managed using readline but through the TUI. The @emph{command}
16002 window is always visible.
16005 The source window shows the source file of the program. The current
16006 line as well as active breakpoints are displayed in this window.
16009 The assembly window shows the disassembly output of the program.
16012 This window shows the processor registers. It detects when
16013 a register is changed and when this is the case, registers that have
16014 changed are highlighted.
16018 The source and assembly windows show the current program position
16019 by highlighting the current line and marking them with the @samp{>} marker.
16020 Breakpoints are also indicated with two markers. A first one
16021 indicates the breakpoint type:
16025 Breakpoint which was hit at least once.
16028 Breakpoint which was never hit.
16031 Hardware breakpoint which was hit at least once.
16034 Hardware breakpoint which was never hit.
16038 The second marker indicates whether the breakpoint is enabled or not:
16042 Breakpoint is enabled.
16045 Breakpoint is disabled.
16049 The source, assembly and register windows are attached to the thread
16050 and the frame position. They are updated when the current thread
16051 changes, when the frame changes or when the program counter changes.
16052 These three windows are arranged by the TUI according to several
16053 layouts. The layout defines which of these three windows are visible.
16054 The following layouts are available:
16064 source and assembly
16067 source and registers
16070 assembly and registers
16074 On top of the command window a status line gives various information
16075 concerning the current process begin debugged. The status line is
16076 updated when the information it shows changes. The following fields
16081 Indicates the current gdb target
16082 (@pxref{Targets, ,Specifying a Debugging Target}).
16085 Gives information about the current process or thread number.
16086 When no process is being debugged, this field is set to @code{No process}.
16089 Gives the current function name for the selected frame.
16090 The name is demangled if demangling is turned on (@pxref{Print Settings}).
16091 When there is no symbol corresponding to the current program counter
16092 the string @code{??} is displayed.
16095 Indicates the current line number for the selected frame.
16096 When the current line number is not known the string @code{??} is displayed.
16099 Indicates the current program counter address.
16104 @section TUI Key Bindings
16105 @cindex TUI key bindings
16107 The TUI installs several key bindings in the readline keymaps
16108 (@pxref{Command Line Editing}).
16109 They allow to leave or enter in the TUI mode or they operate
16110 directly on the TUI layout and windows. The TUI also provides
16111 a @emph{SingleKey} keymap which binds several keys directly to
16112 @value{GDBN} commands. The following key bindings
16113 are installed for both TUI mode and the @value{GDBN} standard mode.
16122 Enter or leave the TUI mode. When the TUI mode is left,
16123 the curses window management is left and @value{GDBN} operates using
16124 its standard mode writing on the terminal directly. When the TUI
16125 mode is entered, the control is given back to the curses windows.
16126 The screen is then refreshed.
16130 Use a TUI layout with only one window. The layout will
16131 either be @samp{source} or @samp{assembly}. When the TUI mode
16132 is not active, it will switch to the TUI mode.
16134 Think of this key binding as the Emacs @kbd{C-x 1} binding.
16138 Use a TUI layout with at least two windows. When the current
16139 layout shows already two windows, a next layout with two windows is used.
16140 When a new layout is chosen, one window will always be common to the
16141 previous layout and the new one.
16143 Think of it as the Emacs @kbd{C-x 2} binding.
16147 Change the active window. The TUI associates several key bindings
16148 (like scrolling and arrow keys) to the active window. This command
16149 gives the focus to the next TUI window.
16151 Think of it as the Emacs @kbd{C-x o} binding.
16155 Use the TUI @emph{SingleKey} keymap that binds single key to gdb commands
16156 (@pxref{TUI Single Key Mode}).
16160 The following key bindings are handled only by the TUI mode:
16165 Scroll the active window one page up.
16169 Scroll the active window one page down.
16173 Scroll the active window one line up.
16177 Scroll the active window one line down.
16181 Scroll the active window one column left.
16185 Scroll the active window one column right.
16189 Refresh the screen.
16193 In the TUI mode, the arrow keys are used by the active window
16194 for scrolling. This means they are available for readline when the
16195 active window is the command window. When the command window
16196 does not have the focus, it is necessary to use other readline
16197 key bindings such as @key{C-p}, @key{C-n}, @key{C-b} and @key{C-f}.
16199 @node TUI Single Key Mode
16200 @section TUI Single Key Mode
16201 @cindex TUI single key mode
16203 The TUI provides a @emph{SingleKey} mode in which it installs a particular
16204 key binding in the readline keymaps to connect single keys to
16208 @kindex c @r{(SingleKey TUI key)}
16212 @kindex d @r{(SingleKey TUI key)}
16216 @kindex f @r{(SingleKey TUI key)}
16220 @kindex n @r{(SingleKey TUI key)}
16224 @kindex q @r{(SingleKey TUI key)}
16226 exit the @emph{SingleKey} mode.
16228 @kindex r @r{(SingleKey TUI key)}
16232 @kindex s @r{(SingleKey TUI key)}
16236 @kindex u @r{(SingleKey TUI key)}
16240 @kindex v @r{(SingleKey TUI key)}
16244 @kindex w @r{(SingleKey TUI key)}
16250 Other keys temporarily switch to the @value{GDBN} command prompt.
16251 The key that was pressed is inserted in the editing buffer so that
16252 it is possible to type most @value{GDBN} commands without interaction
16253 with the TUI @emph{SingleKey} mode. Once the command is entered the TUI
16254 @emph{SingleKey} mode is restored. The only way to permanently leave
16255 this mode is by hitting @key{q} or @samp{@key{C-x} @key{s}}.
16259 @section TUI specific commands
16260 @cindex TUI commands
16262 The TUI has specific commands to control the text windows.
16263 These commands are always available, that is they do not depend on
16264 the current terminal mode in which @value{GDBN} runs. When @value{GDBN}
16265 is in the standard mode, using these commands will automatically switch
16271 List and give the size of all displayed windows.
16275 Display the next layout.
16278 Display the previous layout.
16281 Display the source window only.
16284 Display the assembly window only.
16287 Display the source and assembly window.
16290 Display the register window together with the source or assembly window.
16292 @item focus next | prev | src | asm | regs | split
16294 Set the focus to the named window.
16295 This command allows to change the active window so that scrolling keys
16296 can be affected to another window.
16300 Refresh the screen. This is similar to using @key{C-L} key.
16302 @item tui reg float
16304 Show the floating point registers in the register window.
16306 @item tui reg general
16307 Show the general registers in the register window.
16310 Show the next register group. The list of register groups as well as
16311 their order is target specific. The predefined register groups are the
16312 following: @code{general}, @code{float}, @code{system}, @code{vector},
16313 @code{all}, @code{save}, @code{restore}.
16315 @item tui reg system
16316 Show the system registers in the register window.
16320 Update the source window and the current execution point.
16322 @item winheight @var{name} +@var{count}
16323 @itemx winheight @var{name} -@var{count}
16325 Change the height of the window @var{name} by @var{count}
16326 lines. Positive counts increase the height, while negative counts
16330 @kindex tabset @var{nchars}
16331 Set the width of tab stops to be @var{nchars} characters.
16335 @node TUI Configuration
16336 @section TUI configuration variables
16337 @cindex TUI configuration variables
16339 The TUI has several configuration variables that control the
16340 appearance of windows on the terminal.
16343 @item set tui border-kind @var{kind}
16344 @kindex set tui border-kind
16345 Select the border appearance for the source, assembly and register windows.
16346 The possible values are the following:
16349 Use a space character to draw the border.
16352 Use ascii characters + - and | to draw the border.
16355 Use the Alternate Character Set to draw the border. The border is
16356 drawn using character line graphics if the terminal supports them.
16360 @item set tui active-border-mode @var{mode}
16361 @kindex set tui active-border-mode
16362 Select the attributes to display the border of the active window.
16363 The possible values are @code{normal}, @code{standout}, @code{reverse},
16364 @code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}.
16366 @item set tui border-mode @var{mode}
16367 @kindex set tui border-mode
16368 Select the attributes to display the border of other windows.
16369 The @var{mode} can be one of the following:
16372 Use normal attributes to display the border.
16378 Use reverse video mode.
16381 Use half bright mode.
16383 @item half-standout
16384 Use half bright and standout mode.
16387 Use extra bright or bold mode.
16389 @item bold-standout
16390 Use extra bright or bold and standout mode.
16397 @chapter Using @value{GDBN} under @sc{gnu} Emacs
16400 @cindex @sc{gnu} Emacs
16401 A special interface allows you to use @sc{gnu} Emacs to view (and
16402 edit) the source files for the program you are debugging with
16405 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
16406 executable file you want to debug as an argument. This command starts
16407 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
16408 created Emacs buffer.
16409 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
16411 Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
16416 All ``terminal'' input and output goes through the Emacs buffer.
16419 This applies both to @value{GDBN} commands and their output, and to the input
16420 and output done by the program you are debugging.
16422 This is useful because it means that you can copy the text of previous
16423 commands and input them again; you can even use parts of the output
16426 All the facilities of Emacs' Shell mode are available for interacting
16427 with your program. In particular, you can send signals the usual
16428 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
16433 @value{GDBN} displays source code through Emacs.
16436 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
16437 source file for that frame and puts an arrow (@samp{=>}) at the
16438 left margin of the current line. Emacs uses a separate buffer for
16439 source display, and splits the screen to show both your @value{GDBN} session
16442 Explicit @value{GDBN} @code{list} or search commands still produce output as
16443 usual, but you probably have no reason to use them from Emacs.
16445 If you specify an absolute file name when prompted for the @kbd{M-x
16446 gdb} argument, then Emacs sets your current working directory to where
16447 your program resides. If you only specify the file name, then Emacs
16448 sets your current working directory to to the directory associated
16449 with the previous buffer. In this case, @value{GDBN} may find your
16450 program by searching your environment's @code{PATH} variable, but on
16451 some operating systems it might not find the source. So, although the
16452 @value{GDBN} input and output session proceeds normally, the auxiliary
16453 buffer does not display the current source and line of execution.
16455 The initial working directory of @value{GDBN} is printed on the top
16456 line of the @value{GDBN} I/O buffer and this serves as a default for
16457 the commands that specify files for @value{GDBN} to operate
16458 on. @xref{Files, ,Commands to specify files}.
16460 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
16461 need to call @value{GDBN} by a different name (for example, if you
16462 keep several configurations around, with different names) you can
16463 customize the Emacs variable @code{gud-gdb-command-name} to run the
16466 In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
16467 addition to the standard Shell mode commands:
16471 Describe the features of Emacs' @value{GDBN} Mode.
16474 Execute to another source line, like the @value{GDBN} @code{step} command; also
16475 update the display window to show the current file and location.
16478 Execute to next source line in this function, skipping all function
16479 calls, like the @value{GDBN} @code{next} command. Then update the display window
16480 to show the current file and location.
16483 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
16484 display window accordingly.
16487 Execute until exit from the selected stack frame, like the @value{GDBN}
16488 @code{finish} command.
16491 Continue execution of your program, like the @value{GDBN} @code{continue}
16495 Go up the number of frames indicated by the numeric argument
16496 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
16497 like the @value{GDBN} @code{up} command.
16500 Go down the number of frames indicated by the numeric argument, like the
16501 @value{GDBN} @code{down} command.
16504 In any source file, the Emacs command @kbd{C-x SPC} (@code{gud-break})
16505 tells @value{GDBN} to set a breakpoint on the source line point is on.
16507 If you type @kbd{M-x speedbar}, then Emacs displays a separate frame which
16508 shows a backtrace when the @value{GDBN} I/O buffer is current. Move
16509 point to any frame in the stack and type @key{RET} to make it become the
16510 current frame and display the associated source in the source buffer.
16511 Alternatively, click @kbd{Mouse-2} to make the selected frame become the
16514 If you accidentally delete the source-display buffer, an easy way to get
16515 it back is to type the command @code{f} in the @value{GDBN} buffer, to
16516 request a frame display; when you run under Emacs, this recreates
16517 the source buffer if necessary to show you the context of the current
16520 The source files displayed in Emacs are in ordinary Emacs buffers
16521 which are visiting the source files in the usual way. You can edit
16522 the files with these buffers if you wish; but keep in mind that @value{GDBN}
16523 communicates with Emacs in terms of line numbers. If you add or
16524 delete lines from the text, the line numbers that @value{GDBN} knows cease
16525 to correspond properly with the code.
16527 The description given here is for GNU Emacs version 21.3 and a more
16528 detailed description of its interaction with @value{GDBN} is given in
16529 the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu} Emacs Manual}).
16531 @c The following dropped because Epoch is nonstandard. Reactivate
16532 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
16534 @kindex Emacs Epoch environment
16538 Version 18 of @sc{gnu} Emacs has a built-in window system
16539 called the @code{epoch}
16540 environment. Users of this environment can use a new command,
16541 @code{inspect} which performs identically to @code{print} except that
16542 each value is printed in its own window.
16547 @chapter The @sc{gdb/mi} Interface
16549 @unnumberedsec Function and Purpose
16551 @cindex @sc{gdb/mi}, its purpose
16552 @sc{gdb/mi} is a line based machine oriented text interface to
16553 @value{GDBN} and is activated by specifying using the
16554 @option{--interpreter} command line option (@pxref{Mode Options}). It
16555 is specifically intended to support the development of systems which
16556 use the debugger as just one small component of a larger system.
16558 This chapter is a specification of the @sc{gdb/mi} interface. It is written
16559 in the form of a reference manual.
16561 Note that @sc{gdb/mi} is still under construction, so some of the
16562 features described below are incomplete and subject to change.
16564 @unnumberedsec Notation and Terminology
16566 @cindex notational conventions, for @sc{gdb/mi}
16567 This chapter uses the following notation:
16571 @code{|} separates two alternatives.
16574 @code{[ @var{something} ]} indicates that @var{something} is optional:
16575 it may or may not be given.
16578 @code{( @var{group} )*} means that @var{group} inside the parentheses
16579 may repeat zero or more times.
16582 @code{( @var{group} )+} means that @var{group} inside the parentheses
16583 may repeat one or more times.
16586 @code{"@var{string}"} means a literal @var{string}.
16590 @heading Dependencies
16593 @heading Acknowledgments
16595 In alphabetic order: Andrew Cagney, Fernando Nasser, Stan Shebs and
16599 * GDB/MI Command Syntax::
16600 * GDB/MI Compatibility with CLI::
16601 * GDB/MI Output Records::
16602 * GDB/MI Command Description Format::
16603 * GDB/MI Breakpoint Table Commands::
16604 * GDB/MI Data Manipulation::
16605 * GDB/MI Program Control::
16606 * GDB/MI Miscellaneous Commands::
16608 * GDB/MI Kod Commands::
16609 * GDB/MI Memory Overlay Commands::
16610 * GDB/MI Signal Handling Commands::
16612 * GDB/MI Stack Manipulation::
16613 * GDB/MI Symbol Query::
16614 * GDB/MI Target Manipulation::
16615 * GDB/MI Thread Commands::
16616 * GDB/MI Tracepoint Commands::
16617 * GDB/MI Variable Objects::
16620 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16621 @node GDB/MI Command Syntax
16622 @section @sc{gdb/mi} Command Syntax
16625 * GDB/MI Input Syntax::
16626 * GDB/MI Output Syntax::
16627 * GDB/MI Simple Examples::
16630 @node GDB/MI Input Syntax
16631 @subsection @sc{gdb/mi} Input Syntax
16633 @cindex input syntax for @sc{gdb/mi}
16634 @cindex @sc{gdb/mi}, input syntax
16636 @item @var{command} @expansion{}
16637 @code{@var{cli-command} | @var{mi-command}}
16639 @item @var{cli-command} @expansion{}
16640 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
16641 @var{cli-command} is any existing @value{GDBN} CLI command.
16643 @item @var{mi-command} @expansion{}
16644 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
16645 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
16647 @item @var{token} @expansion{}
16648 "any sequence of digits"
16650 @item @var{option} @expansion{}
16651 @code{"-" @var{parameter} [ " " @var{parameter} ]}
16653 @item @var{parameter} @expansion{}
16654 @code{@var{non-blank-sequence} | @var{c-string}}
16656 @item @var{operation} @expansion{}
16657 @emph{any of the operations described in this chapter}
16659 @item @var{non-blank-sequence} @expansion{}
16660 @emph{anything, provided it doesn't contain special characters such as
16661 "-", @var{nl}, """ and of course " "}
16663 @item @var{c-string} @expansion{}
16664 @code{""" @var{seven-bit-iso-c-string-content} """}
16666 @item @var{nl} @expansion{}
16675 The CLI commands are still handled by the @sc{mi} interpreter; their
16676 output is described below.
16679 The @code{@var{token}}, when present, is passed back when the command
16683 Some @sc{mi} commands accept optional arguments as part of the parameter
16684 list. Each option is identified by a leading @samp{-} (dash) and may be
16685 followed by an optional argument parameter. Options occur first in the
16686 parameter list and can be delimited from normal parameters using
16687 @samp{--} (this is useful when some parameters begin with a dash).
16694 We want easy access to the existing CLI syntax (for debugging).
16697 We want it to be easy to spot a @sc{mi} operation.
16700 @node GDB/MI Output Syntax
16701 @subsection @sc{gdb/mi} Output Syntax
16703 @cindex output syntax of @sc{gdb/mi}
16704 @cindex @sc{gdb/mi}, output syntax
16705 The output from @sc{gdb/mi} consists of zero or more out-of-band records
16706 followed, optionally, by a single result record. This result record
16707 is for the most recent command. The sequence of output records is
16708 terminated by @samp{(@value{GDBP})}.
16710 If an input command was prefixed with a @code{@var{token}} then the
16711 corresponding output for that command will also be prefixed by that same
16715 @item @var{output} @expansion{}
16716 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(@value{GDBP})" @var{nl}}
16718 @item @var{result-record} @expansion{}
16719 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
16721 @item @var{out-of-band-record} @expansion{}
16722 @code{@var{async-record} | @var{stream-record}}
16724 @item @var{async-record} @expansion{}
16725 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
16727 @item @var{exec-async-output} @expansion{}
16728 @code{[ @var{token} ] "*" @var{async-output}}
16730 @item @var{status-async-output} @expansion{}
16731 @code{[ @var{token} ] "+" @var{async-output}}
16733 @item @var{notify-async-output} @expansion{}
16734 @code{[ @var{token} ] "=" @var{async-output}}
16736 @item @var{async-output} @expansion{}
16737 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
16739 @item @var{result-class} @expansion{}
16740 @code{"done" | "running" | "connected" | "error" | "exit"}
16742 @item @var{async-class} @expansion{}
16743 @code{"stopped" | @var{others}} (where @var{others} will be added
16744 depending on the needs---this is still in development).
16746 @item @var{result} @expansion{}
16747 @code{ @var{variable} "=" @var{value}}
16749 @item @var{variable} @expansion{}
16750 @code{ @var{string} }
16752 @item @var{value} @expansion{}
16753 @code{ @var{const} | @var{tuple} | @var{list} }
16755 @item @var{const} @expansion{}
16756 @code{@var{c-string}}
16758 @item @var{tuple} @expansion{}
16759 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
16761 @item @var{list} @expansion{}
16762 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
16763 @var{result} ( "," @var{result} )* "]" }
16765 @item @var{stream-record} @expansion{}
16766 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
16768 @item @var{console-stream-output} @expansion{}
16769 @code{"~" @var{c-string}}
16771 @item @var{target-stream-output} @expansion{}
16772 @code{"@@" @var{c-string}}
16774 @item @var{log-stream-output} @expansion{}
16775 @code{"&" @var{c-string}}
16777 @item @var{nl} @expansion{}
16780 @item @var{token} @expansion{}
16781 @emph{any sequence of digits}.
16789 All output sequences end in a single line containing a period.
16792 The @code{@var{token}} is from the corresponding request. If an execution
16793 command is interrupted by the @samp{-exec-interrupt} command, the
16794 @var{token} associated with the @samp{*stopped} message is the one of the
16795 original execution command, not the one of the interrupt command.
16798 @cindex status output in @sc{gdb/mi}
16799 @var{status-async-output} contains on-going status information about the
16800 progress of a slow operation. It can be discarded. All status output is
16801 prefixed by @samp{+}.
16804 @cindex async output in @sc{gdb/mi}
16805 @var{exec-async-output} contains asynchronous state change on the target
16806 (stopped, started, disappeared). All async output is prefixed by
16810 @cindex notify output in @sc{gdb/mi}
16811 @var{notify-async-output} contains supplementary information that the
16812 client should handle (e.g., a new breakpoint information). All notify
16813 output is prefixed by @samp{=}.
16816 @cindex console output in @sc{gdb/mi}
16817 @var{console-stream-output} is output that should be displayed as is in the
16818 console. It is the textual response to a CLI command. All the console
16819 output is prefixed by @samp{~}.
16822 @cindex target output in @sc{gdb/mi}
16823 @var{target-stream-output} is the output produced by the target program.
16824 All the target output is prefixed by @samp{@@}.
16827 @cindex log output in @sc{gdb/mi}
16828 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
16829 instance messages that should be displayed as part of an error log. All
16830 the log output is prefixed by @samp{&}.
16833 @cindex list output in @sc{gdb/mi}
16834 New @sc{gdb/mi} commands should only output @var{lists} containing
16840 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
16841 details about the various output records.
16843 @node GDB/MI Simple Examples
16844 @subsection Simple Examples of @sc{gdb/mi} Interaction
16845 @cindex @sc{gdb/mi}, simple examples
16847 This subsection presents several simple examples of interaction using
16848 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
16849 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
16850 the output received from @sc{gdb/mi}.
16852 @subsubheading Target Stop
16853 @c Ummm... There is no "-stop" command. This assumes async, no?
16854 Here's an example of stopping the inferior process:
16865 <- *stop,reason="stop",address="0x123",source="a.c:123"
16869 @subsubheading Simple CLI Command
16871 Here's an example of a simple CLI command being passed through
16872 @sc{gdb/mi} and on to the CLI.
16882 @subsubheading Command With Side Effects
16885 -> -symbol-file xyz.exe
16886 <- *breakpoint,nr="3",address="0x123",source="a.c:123"
16890 @subsubheading A Bad Command
16892 Here's what happens if you pass a non-existent command:
16896 <- ^error,msg="Undefined MI command: rubbish"
16900 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16901 @node GDB/MI Compatibility with CLI
16902 @section @sc{gdb/mi} Compatibility with CLI
16904 @cindex compatibility, @sc{gdb/mi} and CLI
16905 @cindex @sc{gdb/mi}, compatibility with CLI
16906 To help users familiar with @value{GDBN}'s existing CLI interface, @sc{gdb/mi}
16907 accepts existing CLI commands. As specified by the syntax, such
16908 commands can be directly entered into the @sc{gdb/mi} interface and @value{GDBN} will
16911 This mechanism is provided as an aid to developers of @sc{gdb/mi}
16912 clients and not as a reliable interface into the CLI. Since the command
16913 is being interpreteted in an environment that assumes @sc{gdb/mi}
16914 behaviour, the exact output of such commands is likely to end up being
16915 an un-supported hybrid of @sc{gdb/mi} and CLI output.
16917 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16918 @node GDB/MI Output Records
16919 @section @sc{gdb/mi} Output Records
16922 * GDB/MI Result Records::
16923 * GDB/MI Stream Records::
16924 * GDB/MI Out-of-band Records::
16927 @node GDB/MI Result Records
16928 @subsection @sc{gdb/mi} Result Records
16930 @cindex result records in @sc{gdb/mi}
16931 @cindex @sc{gdb/mi}, result records
16932 In addition to a number of out-of-band notifications, the response to a
16933 @sc{gdb/mi} command includes one of the following result indications:
16937 @item "^done" [ "," @var{results} ]
16938 The synchronous operation was successful, @code{@var{results}} are the return
16943 @c Is this one correct? Should it be an out-of-band notification?
16944 The asynchronous operation was successfully started. The target is
16947 @item "^error" "," @var{c-string}
16949 The operation failed. The @code{@var{c-string}} contains the corresponding
16953 @node GDB/MI Stream Records
16954 @subsection @sc{gdb/mi} Stream Records
16956 @cindex @sc{gdb/mi}, stream records
16957 @cindex stream records in @sc{gdb/mi}
16958 @value{GDBN} internally maintains a number of output streams: the console, the
16959 target, and the log. The output intended for each of these streams is
16960 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
16962 Each stream record begins with a unique @dfn{prefix character} which
16963 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
16964 Syntax}). In addition to the prefix, each stream record contains a
16965 @code{@var{string-output}}. This is either raw text (with an implicit new
16966 line) or a quoted C string (which does not contain an implicit newline).
16969 @item "~" @var{string-output}
16970 The console output stream contains text that should be displayed in the
16971 CLI console window. It contains the textual responses to CLI commands.
16973 @item "@@" @var{string-output}
16974 The target output stream contains any textual output from the running
16977 @item "&" @var{string-output}
16978 The log stream contains debugging messages being produced by @value{GDBN}'s
16982 @node GDB/MI Out-of-band Records
16983 @subsection @sc{gdb/mi} Out-of-band Records
16985 @cindex out-of-band records in @sc{gdb/mi}
16986 @cindex @sc{gdb/mi}, out-of-band records
16987 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
16988 additional changes that have occurred. Those changes can either be a
16989 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
16990 target activity (e.g., target stopped).
16992 The following is a preliminary list of possible out-of-band records.
16993 In particular, the @var{exec-async-output} records.
16996 @item *stopped,reason="@var{reason}"
16999 @var{reason} can be one of the following:
17002 @item breakpoint-hit
17003 A breakpoint was reached.
17004 @item watchpoint-trigger
17005 A watchpoint was triggered.
17006 @item read-watchpoint-trigger
17007 A read watchpoint was triggered.
17008 @item access-watchpoint-trigger
17009 An access watchpoint was triggered.
17010 @item function-finished
17011 An -exec-finish or similar CLI command was accomplished.
17012 @item location-reached
17013 An -exec-until or similar CLI command was accomplished.
17014 @item watchpoint-scope
17015 A watchpoint has gone out of scope.
17016 @item end-stepping-range
17017 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
17018 similar CLI command was accomplished.
17019 @item exited-signalled
17020 The inferior exited because of a signal.
17022 The inferior exited.
17023 @item exited-normally
17024 The inferior exited normally.
17025 @item signal-received
17026 A signal was received by the inferior.
17030 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17031 @node GDB/MI Command Description Format
17032 @section @sc{gdb/mi} Command Description Format
17034 The remaining sections describe blocks of commands. Each block of
17035 commands is laid out in a fashion similar to this section.
17037 Note the the line breaks shown in the examples are here only for
17038 readability. They don't appear in the real output.
17039 Also note that the commands with a non-available example (N.A.@:) are
17040 not yet implemented.
17042 @subheading Motivation
17044 The motivation for this collection of commands.
17046 @subheading Introduction
17048 A brief introduction to this collection of commands as a whole.
17050 @subheading Commands
17052 For each command in the block, the following is described:
17054 @subsubheading Synopsis
17057 -command @var{args}@dots{}
17060 @subsubheading @value{GDBN} Command
17062 The corresponding @value{GDBN} CLI command.
17064 @subsubheading Result
17066 @subsubheading Out-of-band
17068 @subsubheading Notes
17070 @subsubheading Example
17073 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17074 @node GDB/MI Breakpoint Table Commands
17075 @section @sc{gdb/mi} Breakpoint table commands
17077 @cindex breakpoint commands for @sc{gdb/mi}
17078 @cindex @sc{gdb/mi}, breakpoint commands
17079 This section documents @sc{gdb/mi} commands for manipulating
17082 @subheading The @code{-break-after} Command
17083 @findex -break-after
17085 @subsubheading Synopsis
17088 -break-after @var{number} @var{count}
17091 The breakpoint number @var{number} is not in effect until it has been
17092 hit @var{count} times. To see how this is reflected in the output of
17093 the @samp{-break-list} command, see the description of the
17094 @samp{-break-list} command below.
17096 @subsubheading @value{GDBN} Command
17098 The corresponding @value{GDBN} command is @samp{ignore}.
17100 @subsubheading Example
17105 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",line="5"@}
17112 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17113 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17114 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17115 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17116 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17117 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17118 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17119 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17120 addr="0x000100d0",func="main",file="hello.c",line="5",times="0",
17126 @subheading The @code{-break-catch} Command
17127 @findex -break-catch
17129 @subheading The @code{-break-commands} Command
17130 @findex -break-commands
17134 @subheading The @code{-break-condition} Command
17135 @findex -break-condition
17137 @subsubheading Synopsis
17140 -break-condition @var{number} @var{expr}
17143 Breakpoint @var{number} will stop the program only if the condition in
17144 @var{expr} is true. The condition becomes part of the
17145 @samp{-break-list} output (see the description of the @samp{-break-list}
17148 @subsubheading @value{GDBN} Command
17150 The corresponding @value{GDBN} command is @samp{condition}.
17152 @subsubheading Example
17156 -break-condition 1 1
17160 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17161 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17162 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17163 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17164 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17165 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17166 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17167 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17168 addr="0x000100d0",func="main",file="hello.c",line="5",cond="1",
17169 times="0",ignore="3"@}]@}
17173 @subheading The @code{-break-delete} Command
17174 @findex -break-delete
17176 @subsubheading Synopsis
17179 -break-delete ( @var{breakpoint} )+
17182 Delete the breakpoint(s) whose number(s) are specified in the argument
17183 list. This is obviously reflected in the breakpoint list.
17185 @subsubheading @value{GDBN} command
17187 The corresponding @value{GDBN} command is @samp{delete}.
17189 @subsubheading Example
17197 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
17198 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17199 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17200 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17201 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17202 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17203 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17208 @subheading The @code{-break-disable} Command
17209 @findex -break-disable
17211 @subsubheading Synopsis
17214 -break-disable ( @var{breakpoint} )+
17217 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
17218 break list is now set to @samp{n} for the named @var{breakpoint}(s).
17220 @subsubheading @value{GDBN} Command
17222 The corresponding @value{GDBN} command is @samp{disable}.
17224 @subsubheading Example
17232 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17233 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17234 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17235 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17236 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17237 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17238 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17239 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
17240 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
17244 @subheading The @code{-break-enable} Command
17245 @findex -break-enable
17247 @subsubheading Synopsis
17250 -break-enable ( @var{breakpoint} )+
17253 Enable (previously disabled) @var{breakpoint}(s).
17255 @subsubheading @value{GDBN} Command
17257 The corresponding @value{GDBN} command is @samp{enable}.
17259 @subsubheading Example
17267 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17268 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17269 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17270 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17271 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17272 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17273 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17274 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
17275 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
17279 @subheading The @code{-break-info} Command
17280 @findex -break-info
17282 @subsubheading Synopsis
17285 -break-info @var{breakpoint}
17289 Get information about a single breakpoint.
17291 @subsubheading @value{GDBN} command
17293 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
17295 @subsubheading Example
17298 @subheading The @code{-break-insert} Command
17299 @findex -break-insert
17301 @subsubheading Synopsis
17304 -break-insert [ -t ] [ -h ] [ -r ]
17305 [ -c @var{condition} ] [ -i @var{ignore-count} ]
17306 [ -p @var{thread} ] [ @var{line} | @var{addr} ]
17310 If specified, @var{line}, can be one of:
17317 @item filename:linenum
17318 @item filename:function
17322 The possible optional parameters of this command are:
17326 Insert a tempoary breakpoint.
17328 Insert a hardware breakpoint.
17329 @item -c @var{condition}
17330 Make the breakpoint conditional on @var{condition}.
17331 @item -i @var{ignore-count}
17332 Initialize the @var{ignore-count}.
17334 Insert a regular breakpoint in all the functions whose names match the
17335 given regular expression. Other flags are not applicable to regular
17339 @subsubheading Result
17341 The result is in the form:
17344 ^done,bkptno="@var{number}",func="@var{funcname}",
17345 file="@var{filename}",line="@var{lineno}"
17349 where @var{number} is the @value{GDBN} number for this breakpoint, @var{funcname}
17350 is the name of the function where the breakpoint was inserted,
17351 @var{filename} is the name of the source file which contains this
17352 function, and @var{lineno} is the source line number within that file.
17354 Note: this format is open to change.
17355 @c An out-of-band breakpoint instead of part of the result?
17357 @subsubheading @value{GDBN} Command
17359 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
17360 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
17362 @subsubheading Example
17367 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
17369 -break-insert -t foo
17370 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",line="11"@}
17373 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17374 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17375 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17376 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17377 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17378 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17379 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17380 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17381 addr="0x0001072c", func="main",file="recursive2.c",line="4",times="0"@},
17382 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
17383 addr="0x00010774",func="foo",file="recursive2.c",line="11",times="0"@}]@}
17385 -break-insert -r foo.*
17386 ~int foo(int, int);
17387 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c",line="11"@}
17391 @subheading The @code{-break-list} Command
17392 @findex -break-list
17394 @subsubheading Synopsis
17400 Displays the list of inserted breakpoints, showing the following fields:
17404 number of the breakpoint
17406 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
17408 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
17411 is the breakpoint enabled or no: @samp{y} or @samp{n}
17413 memory location at which the breakpoint is set
17415 logical location of the breakpoint, expressed by function name, file
17418 number of times the breakpoint has been hit
17421 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
17422 @code{body} field is an empty list.
17424 @subsubheading @value{GDBN} Command
17426 The corresponding @value{GDBN} command is @samp{info break}.
17428 @subsubheading Example
17433 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17434 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17435 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17436 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17437 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17438 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17439 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17440 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17441 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
17442 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
17443 addr="0x00010114",func="foo",file="hello.c",line="13",times="0"@}]@}
17447 Here's an example of the result when there are no breakpoints:
17452 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
17453 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17454 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17455 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17456 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17457 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17458 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17463 @subheading The @code{-break-watch} Command
17464 @findex -break-watch
17466 @subsubheading Synopsis
17469 -break-watch [ -a | -r ]
17472 Create a watchpoint. With the @samp{-a} option it will create an
17473 @dfn{access} watchpoint, i.e. a watchpoint that triggers either on a
17474 read from or on a write to the memory location. With the @samp{-r}
17475 option, the watchpoint created is a @dfn{read} watchpoint, i.e. it will
17476 trigger only when the memory location is accessed for reading. Without
17477 either of the options, the watchpoint created is a regular watchpoint,
17478 i.e. it will trigger when the memory location is accessed for writing.
17479 @xref{Set Watchpoints, , Setting watchpoints}.
17481 Note that @samp{-break-list} will report a single list of watchpoints and
17482 breakpoints inserted.
17484 @subsubheading @value{GDBN} Command
17486 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
17489 @subsubheading Example
17491 Setting a watchpoint on a variable in the @code{main} function:
17496 ^done,wpt=@{number="2",exp="x"@}
17500 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
17501 value=@{old="-268439212",new="55"@},
17502 frame=@{func="main",args=[],file="recursive2.c",
17503 fullname="/home/foo/bar/devo/myproject/recursive2.c",line="5"@}
17507 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
17508 the program execution twice: first for the variable changing value, then
17509 for the watchpoint going out of scope.
17514 ^done,wpt=@{number="5",exp="C"@}
17518 ^done,reason="watchpoint-trigger",
17519 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
17520 frame=@{func="callee4",args=[],
17521 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
17522 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
17526 ^done,reason="watchpoint-scope",wpnum="5",
17527 frame=@{func="callee3",args=[@{name="strarg",
17528 value="0x11940 \"A string argument.\""@}],
17529 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
17530 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
17534 Listing breakpoints and watchpoints, at different points in the program
17535 execution. Note that once the watchpoint goes out of scope, it is
17541 ^done,wpt=@{number="2",exp="C"@}
17544 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17545 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17546 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17547 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17548 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17549 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17550 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17551 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17552 addr="0x00010734",func="callee4",
17553 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
17554 bkpt=@{number="2",type="watchpoint",disp="keep",
17555 enabled="y",addr="",what="C",times="0"@}]@}
17559 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
17560 value=@{old="-276895068",new="3"@},
17561 frame=@{func="callee4",args=[],
17562 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
17563 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
17566 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17567 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17568 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17569 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17570 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17571 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17572 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17573 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17574 addr="0x00010734",func="callee4",
17575 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
17576 bkpt=@{number="2",type="watchpoint",disp="keep",
17577 enabled="y",addr="",what="C",times="-5"@}]@}
17581 ^done,reason="watchpoint-scope",wpnum="2",
17582 frame=@{func="callee3",args=[@{name="strarg",
17583 value="0x11940 \"A string argument.\""@}],
17584 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
17585 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
17588 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17589 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17590 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17591 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17592 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17593 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17594 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17595 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17596 addr="0x00010734",func="callee4",
17597 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@}]@}
17601 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17602 @node GDB/MI Data Manipulation
17603 @section @sc{gdb/mi} Data Manipulation
17605 @cindex data manipulation, in @sc{gdb/mi}
17606 @cindex @sc{gdb/mi}, data manipulation
17607 This section describes the @sc{gdb/mi} commands that manipulate data:
17608 examine memory and registers, evaluate expressions, etc.
17610 @c REMOVED FROM THE INTERFACE.
17611 @c @subheading -data-assign
17612 @c Change the value of a program variable. Plenty of side effects.
17613 @c @subsubheading GDB command
17615 @c @subsubheading Example
17618 @subheading The @code{-data-disassemble} Command
17619 @findex -data-disassemble
17621 @subsubheading Synopsis
17625 [ -s @var{start-addr} -e @var{end-addr} ]
17626 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
17634 @item @var{start-addr}
17635 is the beginning address (or @code{$pc})
17636 @item @var{end-addr}
17638 @item @var{filename}
17639 is the name of the file to disassemble
17640 @item @var{linenum}
17641 is the line number to disassemble around
17643 is the the number of disassembly lines to be produced. If it is -1,
17644 the whole function will be disassembled, in case no @var{end-addr} is
17645 specified. If @var{end-addr} is specified as a non-zero value, and
17646 @var{lines} is lower than the number of disassembly lines between
17647 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
17648 displayed; if @var{lines} is higher than the number of lines between
17649 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
17652 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
17656 @subsubheading Result
17658 The output for each instruction is composed of four fields:
17667 Note that whatever included in the instruction field, is not manipulated
17668 directely by @sc{gdb/mi}, i.e. it is not possible to adjust its format.
17670 @subsubheading @value{GDBN} Command
17672 There's no direct mapping from this command to the CLI.
17674 @subsubheading Example
17676 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
17680 -data-disassemble -s $pc -e "$pc + 20" -- 0
17683 @{address="0x000107c0",func-name="main",offset="4",
17684 inst="mov 2, %o0"@},
17685 @{address="0x000107c4",func-name="main",offset="8",
17686 inst="sethi %hi(0x11800), %o2"@},
17687 @{address="0x000107c8",func-name="main",offset="12",
17688 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
17689 @{address="0x000107cc",func-name="main",offset="16",
17690 inst="sethi %hi(0x11800), %o2"@},
17691 @{address="0x000107d0",func-name="main",offset="20",
17692 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
17696 Disassemble the whole @code{main} function. Line 32 is part of
17700 -data-disassemble -f basics.c -l 32 -- 0
17702 @{address="0x000107bc",func-name="main",offset="0",
17703 inst="save %sp, -112, %sp"@},
17704 @{address="0x000107c0",func-name="main",offset="4",
17705 inst="mov 2, %o0"@},
17706 @{address="0x000107c4",func-name="main",offset="8",
17707 inst="sethi %hi(0x11800), %o2"@},
17709 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
17710 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
17714 Disassemble 3 instructions from the start of @code{main}:
17718 -data-disassemble -f basics.c -l 32 -n 3 -- 0
17720 @{address="0x000107bc",func-name="main",offset="0",
17721 inst="save %sp, -112, %sp"@},
17722 @{address="0x000107c0",func-name="main",offset="4",
17723 inst="mov 2, %o0"@},
17724 @{address="0x000107c4",func-name="main",offset="8",
17725 inst="sethi %hi(0x11800), %o2"@}]
17729 Disassemble 3 instructions from the start of @code{main} in mixed mode:
17733 -data-disassemble -f basics.c -l 32 -n 3 -- 1
17735 src_and_asm_line=@{line="31",
17736 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
17737 testsuite/gdb.mi/basics.c",line_asm_insn=[
17738 @{address="0x000107bc",func-name="main",offset="0",
17739 inst="save %sp, -112, %sp"@}]@},
17740 src_and_asm_line=@{line="32",
17741 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
17742 testsuite/gdb.mi/basics.c",line_asm_insn=[
17743 @{address="0x000107c0",func-name="main",offset="4",
17744 inst="mov 2, %o0"@},
17745 @{address="0x000107c4",func-name="main",offset="8",
17746 inst="sethi %hi(0x11800), %o2"@}]@}]
17751 @subheading The @code{-data-evaluate-expression} Command
17752 @findex -data-evaluate-expression
17754 @subsubheading Synopsis
17757 -data-evaluate-expression @var{expr}
17760 Evaluate @var{expr} as an expression. The expression could contain an
17761 inferior function call. The function call will execute synchronously.
17762 If the expression contains spaces, it must be enclosed in double quotes.
17764 @subsubheading @value{GDBN} Command
17766 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
17767 @samp{call}. In @code{gdbtk} only, there's a corresponding
17768 @samp{gdb_eval} command.
17770 @subsubheading Example
17772 In the following example, the numbers that precede the commands are the
17773 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
17774 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
17778 211-data-evaluate-expression A
17781 311-data-evaluate-expression &A
17782 311^done,value="0xefffeb7c"
17784 411-data-evaluate-expression A+3
17787 511-data-evaluate-expression "A + 3"
17793 @subheading The @code{-data-list-changed-registers} Command
17794 @findex -data-list-changed-registers
17796 @subsubheading Synopsis
17799 -data-list-changed-registers
17802 Display a list of the registers that have changed.
17804 @subsubheading @value{GDBN} Command
17806 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
17807 has the corresponding command @samp{gdb_changed_register_list}.
17809 @subsubheading Example
17811 On a PPC MBX board:
17819 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
17820 args=[],file="try.c",fullname="/home/foo/bar/devo/myproject/try.c",line="5"@}
17822 -data-list-changed-registers
17823 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
17824 "10","11","13","14","15","16","17","18","19","20","21","22","23",
17825 "24","25","26","27","28","30","31","64","65","66","67","69"]
17830 @subheading The @code{-data-list-register-names} Command
17831 @findex -data-list-register-names
17833 @subsubheading Synopsis
17836 -data-list-register-names [ ( @var{regno} )+ ]
17839 Show a list of register names for the current target. If no arguments
17840 are given, it shows a list of the names of all the registers. If
17841 integer numbers are given as arguments, it will print a list of the
17842 names of the registers corresponding to the arguments. To ensure
17843 consistency between a register name and its number, the output list may
17844 include empty register names.
17846 @subsubheading @value{GDBN} Command
17848 @value{GDBN} does not have a command which corresponds to
17849 @samp{-data-list-register-names}. In @code{gdbtk} there is a
17850 corresponding command @samp{gdb_regnames}.
17852 @subsubheading Example
17854 For the PPC MBX board:
17857 -data-list-register-names
17858 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
17859 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
17860 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
17861 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
17862 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
17863 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
17864 "", "pc","ps","cr","lr","ctr","xer"]
17866 -data-list-register-names 1 2 3
17867 ^done,register-names=["r1","r2","r3"]
17871 @subheading The @code{-data-list-register-values} Command
17872 @findex -data-list-register-values
17874 @subsubheading Synopsis
17877 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
17880 Display the registers' contents. @var{fmt} is the format according to
17881 which the registers' contents are to be returned, followed by an optional
17882 list of numbers specifying the registers to display. A missing list of
17883 numbers indicates that the contents of all the registers must be returned.
17885 Allowed formats for @var{fmt} are:
17902 @subsubheading @value{GDBN} Command
17904 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
17905 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
17907 @subsubheading Example
17909 For a PPC MBX board (note: line breaks are for readability only, they
17910 don't appear in the actual output):
17914 -data-list-register-values r 64 65
17915 ^done,register-values=[@{number="64",value="0xfe00a300"@},
17916 @{number="65",value="0x00029002"@}]
17918 -data-list-register-values x
17919 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
17920 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
17921 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
17922 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
17923 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
17924 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
17925 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
17926 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
17927 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
17928 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
17929 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
17930 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
17931 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
17932 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
17933 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
17934 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
17935 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
17936 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
17937 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
17938 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
17939 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
17940 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
17941 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
17942 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
17943 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
17944 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
17945 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
17946 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
17947 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
17948 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
17949 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
17950 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
17951 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
17952 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
17953 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
17954 @{number="69",value="0x20002b03"@}]
17959 @subheading The @code{-data-read-memory} Command
17960 @findex -data-read-memory
17962 @subsubheading Synopsis
17965 -data-read-memory [ -o @var{byte-offset} ]
17966 @var{address} @var{word-format} @var{word-size}
17967 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
17974 @item @var{address}
17975 An expression specifying the address of the first memory word to be
17976 read. Complex expressions containing embedded white space should be
17977 quoted using the C convention.
17979 @item @var{word-format}
17980 The format to be used to print the memory words. The notation is the
17981 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
17984 @item @var{word-size}
17985 The size of each memory word in bytes.
17987 @item @var{nr-rows}
17988 The number of rows in the output table.
17990 @item @var{nr-cols}
17991 The number of columns in the output table.
17994 If present, indicates that each row should include an @sc{ascii} dump. The
17995 value of @var{aschar} is used as a padding character when a byte is not a
17996 member of the printable @sc{ascii} character set (printable @sc{ascii}
17997 characters are those whose code is between 32 and 126, inclusively).
17999 @item @var{byte-offset}
18000 An offset to add to the @var{address} before fetching memory.
18003 This command displays memory contents as a table of @var{nr-rows} by
18004 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
18005 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
18006 (returned as @samp{total-bytes}). Should less than the requested number
18007 of bytes be returned by the target, the missing words are identified
18008 using @samp{N/A}. The number of bytes read from the target is returned
18009 in @samp{nr-bytes} and the starting address used to read memory in
18012 The address of the next/previous row or page is available in
18013 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
18016 @subsubheading @value{GDBN} Command
18018 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
18019 @samp{gdb_get_mem} memory read command.
18021 @subsubheading Example
18023 Read six bytes of memory starting at @code{bytes+6} but then offset by
18024 @code{-6} bytes. Format as three rows of two columns. One byte per
18025 word. Display each word in hex.
18029 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
18030 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
18031 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
18032 prev-page="0x0000138a",memory=[
18033 @{addr="0x00001390",data=["0x00","0x01"]@},
18034 @{addr="0x00001392",data=["0x02","0x03"]@},
18035 @{addr="0x00001394",data=["0x04","0x05"]@}]
18039 Read two bytes of memory starting at address @code{shorts + 64} and
18040 display as a single word formatted in decimal.
18044 5-data-read-memory shorts+64 d 2 1 1
18045 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
18046 next-row="0x00001512",prev-row="0x0000150e",
18047 next-page="0x00001512",prev-page="0x0000150e",memory=[
18048 @{addr="0x00001510",data=["128"]@}]
18052 Read thirty two bytes of memory starting at @code{bytes+16} and format
18053 as eight rows of four columns. Include a string encoding with @samp{x}
18054 used as the non-printable character.
18058 4-data-read-memory bytes+16 x 1 8 4 x
18059 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
18060 next-row="0x000013c0",prev-row="0x0000139c",
18061 next-page="0x000013c0",prev-page="0x00001380",memory=[
18062 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
18063 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
18064 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
18065 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
18066 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
18067 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
18068 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
18069 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
18073 @subheading The @code{-display-delete} Command
18074 @findex -display-delete
18076 @subsubheading Synopsis
18079 -display-delete @var{number}
18082 Delete the display @var{number}.
18084 @subsubheading @value{GDBN} Command
18086 The corresponding @value{GDBN} command is @samp{delete display}.
18088 @subsubheading Example
18092 @subheading The @code{-display-disable} Command
18093 @findex -display-disable
18095 @subsubheading Synopsis
18098 -display-disable @var{number}
18101 Disable display @var{number}.
18103 @subsubheading @value{GDBN} Command
18105 The corresponding @value{GDBN} command is @samp{disable display}.
18107 @subsubheading Example
18111 @subheading The @code{-display-enable} Command
18112 @findex -display-enable
18114 @subsubheading Synopsis
18117 -display-enable @var{number}
18120 Enable display @var{number}.
18122 @subsubheading @value{GDBN} Command
18124 The corresponding @value{GDBN} command is @samp{enable display}.
18126 @subsubheading Example
18130 @subheading The @code{-display-insert} Command
18131 @findex -display-insert
18133 @subsubheading Synopsis
18136 -display-insert @var{expression}
18139 Display @var{expression} every time the program stops.
18141 @subsubheading @value{GDBN} Command
18143 The corresponding @value{GDBN} command is @samp{display}.
18145 @subsubheading Example
18149 @subheading The @code{-display-list} Command
18150 @findex -display-list
18152 @subsubheading Synopsis
18158 List the displays. Do not show the current values.
18160 @subsubheading @value{GDBN} Command
18162 The corresponding @value{GDBN} command is @samp{info display}.
18164 @subsubheading Example
18168 @subheading The @code{-environment-cd} Command
18169 @findex -environment-cd
18171 @subsubheading Synopsis
18174 -environment-cd @var{pathdir}
18177 Set @value{GDBN}'s working directory.
18179 @subsubheading @value{GDBN} Command
18181 The corresponding @value{GDBN} command is @samp{cd}.
18183 @subsubheading Example
18187 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18193 @subheading The @code{-environment-directory} Command
18194 @findex -environment-directory
18196 @subsubheading Synopsis
18199 -environment-directory [ -r ] [ @var{pathdir} ]+
18202 Add directories @var{pathdir} to beginning of search path for source files.
18203 If the @samp{-r} option is used, the search path is reset to the default
18204 search path. If directories @var{pathdir} are supplied in addition to the
18205 @samp{-r} option, the search path is first reset and then addition
18207 Multiple directories may be specified, separated by blanks. Specifying
18208 multiple directories in a single command
18209 results in the directories added to the beginning of the
18210 search path in the same order they were presented in the command.
18211 If blanks are needed as
18212 part of a directory name, double-quotes should be used around
18213 the name. In the command output, the path will show up separated
18214 by the system directory-separator character. The directory-seperator
18215 character must not be used
18216 in any directory name.
18217 If no directories are specified, the current search path is displayed.
18219 @subsubheading @value{GDBN} Command
18221 The corresponding @value{GDBN} command is @samp{dir}.
18223 @subsubheading Example
18227 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18228 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18230 -environment-directory ""
18231 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18233 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
18234 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
18236 -environment-directory -r
18237 ^done,source-path="$cdir:$cwd"
18242 @subheading The @code{-environment-path} Command
18243 @findex -environment-path
18245 @subsubheading Synopsis
18248 -environment-path [ -r ] [ @var{pathdir} ]+
18251 Add directories @var{pathdir} to beginning of search path for object files.
18252 If the @samp{-r} option is used, the search path is reset to the original
18253 search path that existed at gdb start-up. If directories @var{pathdir} are
18254 supplied in addition to the
18255 @samp{-r} option, the search path is first reset and then addition
18257 Multiple directories may be specified, separated by blanks. Specifying
18258 multiple directories in a single command
18259 results in the directories added to the beginning of the
18260 search path in the same order they were presented in the command.
18261 If blanks are needed as
18262 part of a directory name, double-quotes should be used around
18263 the name. In the command output, the path will show up separated
18264 by the system directory-separator character. The directory-seperator
18265 character must not be used
18266 in any directory name.
18267 If no directories are specified, the current path is displayed.
18270 @subsubheading @value{GDBN} Command
18272 The corresponding @value{GDBN} command is @samp{path}.
18274 @subsubheading Example
18279 ^done,path="/usr/bin"
18281 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
18282 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
18284 -environment-path -r /usr/local/bin
18285 ^done,path="/usr/local/bin:/usr/bin"
18290 @subheading The @code{-environment-pwd} Command
18291 @findex -environment-pwd
18293 @subsubheading Synopsis
18299 Show the current working directory.
18301 @subsubheading @value{GDBN} command
18303 The corresponding @value{GDBN} command is @samp{pwd}.
18305 @subsubheading Example
18310 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
18314 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18315 @node GDB/MI Program Control
18316 @section @sc{gdb/mi} Program control
18318 @subsubheading Program termination
18320 As a result of execution, the inferior program can run to completion, if
18321 it doesn't encounter any breakpoints. In this case the output will
18322 include an exit code, if the program has exited exceptionally.
18324 @subsubheading Examples
18327 Program exited normally:
18335 *stopped,reason="exited-normally"
18340 Program exited exceptionally:
18348 *stopped,reason="exited",exit-code="01"
18352 Another way the program can terminate is if it receives a signal such as
18353 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
18357 *stopped,reason="exited-signalled",signal-name="SIGINT",
18358 signal-meaning="Interrupt"
18362 @subheading The @code{-exec-abort} Command
18363 @findex -exec-abort
18365 @subsubheading Synopsis
18371 Kill the inferior running program.
18373 @subsubheading @value{GDBN} Command
18375 The corresponding @value{GDBN} command is @samp{kill}.
18377 @subsubheading Example
18381 @subheading The @code{-exec-arguments} Command
18382 @findex -exec-arguments
18384 @subsubheading Synopsis
18387 -exec-arguments @var{args}
18390 Set the inferior program arguments, to be used in the next
18393 @subsubheading @value{GDBN} Command
18395 The corresponding @value{GDBN} command is @samp{set args}.
18397 @subsubheading Example
18400 Don't have one around.
18403 @subheading The @code{-exec-continue} Command
18404 @findex -exec-continue
18406 @subsubheading Synopsis
18412 Asynchronous command. Resumes the execution of the inferior program
18413 until a breakpoint is encountered, or until the inferior exits.
18415 @subsubheading @value{GDBN} Command
18417 The corresponding @value{GDBN} corresponding is @samp{continue}.
18419 @subsubheading Example
18426 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
18427 file="hello.c",fullname="/home/foo/bar/devo/myproject/hello.c",line="13"@}
18432 @subheading The @code{-exec-finish} Command
18433 @findex -exec-finish
18435 @subsubheading Synopsis
18441 Asynchronous command. Resumes the execution of the inferior program
18442 until the current function is exited. Displays the results returned by
18445 @subsubheading @value{GDBN} Command
18447 The corresponding @value{GDBN} command is @samp{finish}.
18449 @subsubheading Example
18451 Function returning @code{void}.
18458 *stopped,reason="function-finished",frame=@{func="main",args=[],
18459 file="hello.c",fullname="/home/foo/bar/devo/myproject/hello.c",line="7"@}
18463 Function returning other than @code{void}. The name of the internal
18464 @value{GDBN} variable storing the result is printed, together with the
18471 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
18472 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
18473 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
18474 gdb-result-var="$1",return-value="0"
18479 @subheading The @code{-exec-interrupt} Command
18480 @findex -exec-interrupt
18482 @subsubheading Synopsis
18488 Asynchronous command. Interrupts the background execution of the target.
18489 Note how the token associated with the stop message is the one for the
18490 execution command that has been interrupted. The token for the interrupt
18491 itself only appears in the @samp{^done} output. If the user is trying to
18492 interrupt a non-running program, an error message will be printed.
18494 @subsubheading @value{GDBN} Command
18496 The corresponding @value{GDBN} command is @samp{interrupt}.
18498 @subsubheading Example
18509 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
18510 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
18511 fullname="/home/foo/bar/devo/myproject/try.c",line="13"@}
18516 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
18521 @subheading The @code{-exec-next} Command
18524 @subsubheading Synopsis
18530 Asynchronous command. Resumes execution of the inferior program, stopping
18531 when the beginning of the next source line is reached.
18533 @subsubheading @value{GDBN} Command
18535 The corresponding @value{GDBN} command is @samp{next}.
18537 @subsubheading Example
18543 *stopped,reason="end-stepping-range",line="8",file="hello.c"
18548 @subheading The @code{-exec-next-instruction} Command
18549 @findex -exec-next-instruction
18551 @subsubheading Synopsis
18554 -exec-next-instruction
18557 Asynchronous command. Executes one machine instruction. If the
18558 instruction is a function call continues until the function returns. If
18559 the program stops at an instruction in the middle of a source line, the
18560 address will be printed as well.
18562 @subsubheading @value{GDBN} Command
18564 The corresponding @value{GDBN} command is @samp{nexti}.
18566 @subsubheading Example
18570 -exec-next-instruction
18574 *stopped,reason="end-stepping-range",
18575 addr="0x000100d4",line="5",file="hello.c"
18580 @subheading The @code{-exec-return} Command
18581 @findex -exec-return
18583 @subsubheading Synopsis
18589 Makes current function return immediately. Doesn't execute the inferior.
18590 Displays the new current frame.
18592 @subsubheading @value{GDBN} Command
18594 The corresponding @value{GDBN} command is @samp{return}.
18596 @subsubheading Example
18600 200-break-insert callee4
18601 200^done,bkpt=@{number="1",addr="0x00010734",
18602 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
18607 000*stopped,reason="breakpoint-hit",bkptno="1",
18608 frame=@{func="callee4",args=[],
18609 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18610 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
18616 111^done,frame=@{level="0",func="callee3",
18617 args=[@{name="strarg",
18618 value="0x11940 \"A string argument.\""@}],
18619 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18620 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18625 @subheading The @code{-exec-run} Command
18628 @subsubheading Synopsis
18634 Asynchronous command. Starts execution of the inferior from the
18635 beginning. The inferior executes until either a breakpoint is
18636 encountered or the program exits.
18638 @subsubheading @value{GDBN} Command
18640 The corresponding @value{GDBN} command is @samp{run}.
18642 @subsubheading Example
18647 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
18652 *stopped,reason="breakpoint-hit",bkptno="1",
18653 frame=@{func="main",args=[],file="recursive2.c",
18654 fullname="/home/foo/bar/devo/myproject/recursive2.c",line="4"@}
18659 @subheading The @code{-exec-show-arguments} Command
18660 @findex -exec-show-arguments
18662 @subsubheading Synopsis
18665 -exec-show-arguments
18668 Print the arguments of the program.
18670 @subsubheading @value{GDBN} Command
18672 The corresponding @value{GDBN} command is @samp{show args}.
18674 @subsubheading Example
18677 @c @subheading -exec-signal
18679 @subheading The @code{-exec-step} Command
18682 @subsubheading Synopsis
18688 Asynchronous command. Resumes execution of the inferior program, stopping
18689 when the beginning of the next source line is reached, if the next
18690 source line is not a function call. If it is, stop at the first
18691 instruction of the called function.
18693 @subsubheading @value{GDBN} Command
18695 The corresponding @value{GDBN} command is @samp{step}.
18697 @subsubheading Example
18699 Stepping into a function:
18705 *stopped,reason="end-stepping-range",
18706 frame=@{func="foo",args=[@{name="a",value="10"@},
18707 @{name="b",value="0"@}],file="recursive2.c",
18708 fullname="/home/foo/bar/devo/myproject/recursive2.c",line="11"@}
18718 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
18723 @subheading The @code{-exec-step-instruction} Command
18724 @findex -exec-step-instruction
18726 @subsubheading Synopsis
18729 -exec-step-instruction
18732 Asynchronous command. Resumes the inferior which executes one machine
18733 instruction. The output, once @value{GDBN} has stopped, will vary depending on
18734 whether we have stopped in the middle of a source line or not. In the
18735 former case, the address at which the program stopped will be printed as
18738 @subsubheading @value{GDBN} Command
18740 The corresponding @value{GDBN} command is @samp{stepi}.
18742 @subsubheading Example
18746 -exec-step-instruction
18750 *stopped,reason="end-stepping-range",
18751 frame=@{func="foo",args=[],file="try.c",
18752 fullname="/home/foo/bar/devo/myproject/try.c",line="10"@}
18754 -exec-step-instruction
18758 *stopped,reason="end-stepping-range",
18759 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
18760 fullname="/home/foo/bar/devo/myproject/try.c",line="10"@}
18765 @subheading The @code{-exec-until} Command
18766 @findex -exec-until
18768 @subsubheading Synopsis
18771 -exec-until [ @var{location} ]
18774 Asynchronous command. Executes the inferior until the @var{location}
18775 specified in the argument is reached. If there is no argument, the inferior
18776 executes until a source line greater than the current one is reached.
18777 The reason for stopping in this case will be @samp{location-reached}.
18779 @subsubheading @value{GDBN} Command
18781 The corresponding @value{GDBN} command is @samp{until}.
18783 @subsubheading Example
18787 -exec-until recursive2.c:6
18791 *stopped,reason="location-reached",frame=@{func="main",args=[],
18792 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="6"@}
18797 @subheading -file-clear
18798 Is this going away????
18802 @subheading The @code{-file-exec-and-symbols} Command
18803 @findex -file-exec-and-symbols
18805 @subsubheading Synopsis
18808 -file-exec-and-symbols @var{file}
18811 Specify the executable file to be debugged. This file is the one from
18812 which the symbol table is also read. If no file is specified, the
18813 command clears the executable and symbol information. If breakpoints
18814 are set when using this command with no arguments, @value{GDBN} will produce
18815 error messages. Otherwise, no output is produced, except a completion
18818 @subsubheading @value{GDBN} Command
18820 The corresponding @value{GDBN} command is @samp{file}.
18822 @subsubheading Example
18826 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
18832 @subheading The @code{-file-exec-file} Command
18833 @findex -file-exec-file
18835 @subsubheading Synopsis
18838 -file-exec-file @var{file}
18841 Specify the executable file to be debugged. Unlike
18842 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
18843 from this file. If used without argument, @value{GDBN} clears the information
18844 about the executable file. No output is produced, except a completion
18847 @subsubheading @value{GDBN} Command
18849 The corresponding @value{GDBN} command is @samp{exec-file}.
18851 @subsubheading Example
18855 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
18861 @subheading The @code{-file-list-exec-sections} Command
18862 @findex -file-list-exec-sections
18864 @subsubheading Synopsis
18867 -file-list-exec-sections
18870 List the sections of the current executable file.
18872 @subsubheading @value{GDBN} Command
18874 The @value{GDBN} command @samp{info file} shows, among the rest, the same
18875 information as this command. @code{gdbtk} has a corresponding command
18876 @samp{gdb_load_info}.
18878 @subsubheading Example
18882 @subheading The @code{-file-list-exec-source-file} Command
18883 @findex -file-list-exec-source-file
18885 @subsubheading Synopsis
18888 -file-list-exec-source-file
18891 List the line number, the current source file, and the absolute path
18892 to the current source file for the current executable.
18894 @subsubheading @value{GDBN} Command
18896 There's no @value{GDBN} command which directly corresponds to this one.
18898 @subsubheading Example
18902 123-file-list-exec-source-file
18903 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
18908 @subheading The @code{-file-list-exec-source-files} Command
18909 @findex -file-list-exec-source-files
18911 @subsubheading Synopsis
18914 -file-list-exec-source-files
18917 List the source files for the current executable.
18919 It will always output the filename, but only when GDB can find the absolute
18920 file name of a source file, will it output the fullname.
18922 @subsubheading @value{GDBN} Command
18924 There's no @value{GDBN} command which directly corresponds to this one.
18925 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
18927 @subsubheading Example
18930 -file-list-exec-source-files
18932 @{file=foo.c,fullname=/home/foo.c@},
18933 @{file=/home/bar.c,fullname=/home/bar.c@},
18934 @{file=gdb_could_not_find_fullpath.c@}]
18938 @subheading The @code{-file-list-shared-libraries} Command
18939 @findex -file-list-shared-libraries
18941 @subsubheading Synopsis
18944 -file-list-shared-libraries
18947 List the shared libraries in the program.
18949 @subsubheading @value{GDBN} Command
18951 The corresponding @value{GDBN} command is @samp{info shared}.
18953 @subsubheading Example
18957 @subheading The @code{-file-list-symbol-files} Command
18958 @findex -file-list-symbol-files
18960 @subsubheading Synopsis
18963 -file-list-symbol-files
18968 @subsubheading @value{GDBN} Command
18970 The corresponding @value{GDBN} command is @samp{info file} (part of it).
18972 @subsubheading Example
18976 @subheading The @code{-file-symbol-file} Command
18977 @findex -file-symbol-file
18979 @subsubheading Synopsis
18982 -file-symbol-file @var{file}
18985 Read symbol table info from the specified @var{file} argument. When
18986 used without arguments, clears @value{GDBN}'s symbol table info. No output is
18987 produced, except for a completion notification.
18989 @subsubheading @value{GDBN} Command
18991 The corresponding @value{GDBN} command is @samp{symbol-file}.
18993 @subsubheading Example
18997 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
19002 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19003 @node GDB/MI Miscellaneous Commands
19004 @section Miscellaneous @value{GDBN} commands in @sc{gdb/mi}
19006 @c @subheading -gdb-complete
19008 @subheading The @code{-gdb-exit} Command
19011 @subsubheading Synopsis
19017 Exit @value{GDBN} immediately.
19019 @subsubheading @value{GDBN} Command
19021 Approximately corresponds to @samp{quit}.
19023 @subsubheading Example
19030 @subheading The @code{-gdb-set} Command
19033 @subsubheading Synopsis
19039 Set an internal @value{GDBN} variable.
19040 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
19042 @subsubheading @value{GDBN} Command
19044 The corresponding @value{GDBN} command is @samp{set}.
19046 @subsubheading Example
19056 @subheading The @code{-gdb-show} Command
19059 @subsubheading Synopsis
19065 Show the current value of a @value{GDBN} variable.
19067 @subsubheading @value{GDBN} command
19069 The corresponding @value{GDBN} command is @samp{show}.
19071 @subsubheading Example
19080 @c @subheading -gdb-source
19083 @subheading The @code{-gdb-version} Command
19084 @findex -gdb-version
19086 @subsubheading Synopsis
19092 Show version information for @value{GDBN}. Used mostly in testing.
19094 @subsubheading @value{GDBN} Command
19096 There's no equivalent @value{GDBN} command. @value{GDBN} by default shows this
19097 information when you start an interactive session.
19099 @subsubheading Example
19101 @c This example modifies the actual output from GDB to avoid overfull
19107 ~Copyright 2000 Free Software Foundation, Inc.
19108 ~GDB is free software, covered by the GNU General Public License, and
19109 ~you are welcome to change it and/or distribute copies of it under
19110 ~ certain conditions.
19111 ~Type "show copying" to see the conditions.
19112 ~There is absolutely no warranty for GDB. Type "show warranty" for
19114 ~This GDB was configured as
19115 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
19120 @subheading The @code{-interpreter-exec} Command
19121 @findex -interpreter-exec
19123 @subheading Synopsis
19126 -interpreter-exec @var{interpreter} @var{command}
19129 Execute the specified @var{command} in the given @var{interpreter}.
19131 @subheading @value{GDBN} Command
19133 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
19135 @subheading Example
19139 -interpreter-exec console "break main"
19140 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
19141 &"During symbol reading, bad structure-type format.\n"
19142 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
19148 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19149 @node GDB/MI Kod Commands
19150 @section @sc{gdb/mi} Kod Commands
19152 The Kod commands are not implemented.
19154 @c @subheading -kod-info
19156 @c @subheading -kod-list
19158 @c @subheading -kod-list-object-types
19160 @c @subheading -kod-show
19162 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19163 @node GDB/MI Memory Overlay Commands
19164 @section @sc{gdb/mi} Memory Overlay Commands
19166 The memory overlay commands are not implemented.
19168 @c @subheading -overlay-auto
19170 @c @subheading -overlay-list-mapping-state
19172 @c @subheading -overlay-list-overlays
19174 @c @subheading -overlay-map
19176 @c @subheading -overlay-off
19178 @c @subheading -overlay-on
19180 @c @subheading -overlay-unmap
19182 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19183 @node GDB/MI Signal Handling Commands
19184 @section @sc{gdb/mi} Signal Handling Commands
19186 Signal handling commands are not implemented.
19188 @c @subheading -signal-handle
19190 @c @subheading -signal-list-handle-actions
19192 @c @subheading -signal-list-signal-types
19196 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19197 @node GDB/MI Stack Manipulation
19198 @section @sc{gdb/mi} Stack Manipulation Commands
19200 @subheading The @code{-stack-info-depth} Command
19201 @findex -stack-info-depth
19203 @subsubheading Synopsis
19206 -stack-info-depth [ @var{max-depth} ]
19209 Return the depth of the stack. If the integer argument @var{max-depth}
19210 is specified, do not count beyond @var{max-depth} frames.
19212 @subsubheading @value{GDBN} Command
19214 There's no equivalent @value{GDBN} command.
19216 @subsubheading Example
19218 For a stack with frame levels 0 through 11:
19225 -stack-info-depth 4
19228 -stack-info-depth 12
19231 -stack-info-depth 11
19234 -stack-info-depth 13
19239 @subheading The @code{-stack-list-arguments} Command
19240 @findex -stack-list-arguments
19242 @subsubheading Synopsis
19245 -stack-list-arguments @var{show-values}
19246 [ @var{low-frame} @var{high-frame} ]
19249 Display a list of the arguments for the frames between @var{low-frame}
19250 and @var{high-frame} (inclusive). If @var{low-frame} and
19251 @var{high-frame} are not provided, list the arguments for the whole call
19254 The @var{show-values} argument must have a value of 0 or 1. A value of
19255 0 means that only the names of the arguments are listed, a value of 1
19256 means that both names and values of the arguments are printed.
19258 @subsubheading @value{GDBN} Command
19260 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
19261 @samp{gdb_get_args} command which partially overlaps with the
19262 functionality of @samp{-stack-list-arguments}.
19264 @subsubheading Example
19271 frame=@{level="0",addr="0x00010734",func="callee4",
19272 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19273 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
19274 frame=@{level="1",addr="0x0001076c",func="callee3",
19275 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19276 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
19277 frame=@{level="2",addr="0x0001078c",func="callee2",
19278 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19279 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
19280 frame=@{level="3",addr="0x000107b4",func="callee1",
19281 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19282 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
19283 frame=@{level="4",addr="0x000107e0",func="main",
19284 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19285 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
19287 -stack-list-arguments 0
19290 frame=@{level="0",args=[]@},
19291 frame=@{level="1",args=[name="strarg"]@},
19292 frame=@{level="2",args=[name="intarg",name="strarg"]@},
19293 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
19294 frame=@{level="4",args=[]@}]
19296 -stack-list-arguments 1
19299 frame=@{level="0",args=[]@},
19301 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19302 frame=@{level="2",args=[
19303 @{name="intarg",value="2"@},
19304 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19305 @{frame=@{level="3",args=[
19306 @{name="intarg",value="2"@},
19307 @{name="strarg",value="0x11940 \"A string argument.\""@},
19308 @{name="fltarg",value="3.5"@}]@},
19309 frame=@{level="4",args=[]@}]
19311 -stack-list-arguments 0 2 2
19312 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
19314 -stack-list-arguments 1 2 2
19315 ^done,stack-args=[frame=@{level="2",
19316 args=[@{name="intarg",value="2"@},
19317 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
19321 @c @subheading -stack-list-exception-handlers
19324 @subheading The @code{-stack-list-frames} Command
19325 @findex -stack-list-frames
19327 @subsubheading Synopsis
19330 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
19333 List the frames currently on the stack. For each frame it displays the
19338 The frame number, 0 being the topmost frame, i.e. the innermost function.
19340 The @code{$pc} value for that frame.
19344 File name of the source file where the function lives.
19346 Line number corresponding to the @code{$pc}.
19349 If invoked without arguments, this command prints a backtrace for the
19350 whole stack. If given two integer arguments, it shows the frames whose
19351 levels are between the two arguments (inclusive). If the two arguments
19352 are equal, it shows the single frame at the corresponding level.
19354 @subsubheading @value{GDBN} Command
19356 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
19358 @subsubheading Example
19360 Full stack backtrace:
19366 [frame=@{level="0",addr="0x0001076c",func="foo",
19367 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="11"@},
19368 frame=@{level="1",addr="0x000107a4",func="foo",
19369 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19370 frame=@{level="2",addr="0x000107a4",func="foo",
19371 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19372 frame=@{level="3",addr="0x000107a4",func="foo",
19373 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19374 frame=@{level="4",addr="0x000107a4",func="foo",
19375 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19376 frame=@{level="5",addr="0x000107a4",func="foo",
19377 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19378 frame=@{level="6",addr="0x000107a4",func="foo",
19379 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19380 frame=@{level="7",addr="0x000107a4",func="foo",
19381 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19382 frame=@{level="8",addr="0x000107a4",func="foo",
19383 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19384 frame=@{level="9",addr="0x000107a4",func="foo",
19385 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19386 frame=@{level="10",addr="0x000107a4",func="foo",
19387 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19388 frame=@{level="11",addr="0x00010738",func="main",
19389 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="4"@}]
19393 Show frames between @var{low_frame} and @var{high_frame}:
19397 -stack-list-frames 3 5
19399 [frame=@{level="3",addr="0x000107a4",func="foo",
19400 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19401 frame=@{level="4",addr="0x000107a4",func="foo",
19402 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19403 frame=@{level="5",addr="0x000107a4",func="foo",
19404 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@}]
19408 Show a single frame:
19412 -stack-list-frames 3 3
19414 [frame=@{level="3",addr="0x000107a4",func="foo",
19415 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@}]
19420 @subheading The @code{-stack-list-locals} Command
19421 @findex -stack-list-locals
19423 @subsubheading Synopsis
19426 -stack-list-locals @var{print-values}
19429 Display the local variable names for the current frame. With an
19430 argument of 0 or @code{--no-values}, prints only the names of the variables.
19431 With argument of 1 or @code{--all-values}, prints also their values. With
19432 argument of 2 or @code{--simple-values}, prints the name, type and value for
19433 simple data types and the name and type for arrays, structures and
19434 unions. In this last case, the idea is that the user can see the
19435 value of simple data types immediately and he can create variable
19436 objects for other data types if he wishes to explore their values in
19439 @subsubheading @value{GDBN} Command
19441 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
19443 @subsubheading Example
19447 -stack-list-locals 0
19448 ^done,locals=[name="A",name="B",name="C"]
19450 -stack-list-locals --all-values
19451 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
19452 @{name="C",value="@{1, 2, 3@}"@}]
19453 -stack-list-locals --simple-values
19454 ^done,locals=[@{name="A",type="int",value="1"@},
19455 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
19460 @subheading The @code{-stack-select-frame} Command
19461 @findex -stack-select-frame
19463 @subsubheading Synopsis
19466 -stack-select-frame @var{framenum}
19469 Change the current frame. Select a different frame @var{framenum} on
19472 @subsubheading @value{GDBN} Command
19474 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
19475 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
19477 @subsubheading Example
19481 -stack-select-frame 2
19486 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19487 @node GDB/MI Symbol Query
19488 @section @sc{gdb/mi} Symbol Query Commands
19491 @subheading The @code{-symbol-info-address} Command
19492 @findex -symbol-info-address
19494 @subsubheading Synopsis
19497 -symbol-info-address @var{symbol}
19500 Describe where @var{symbol} is stored.
19502 @subsubheading @value{GDBN} Command
19504 The corresponding @value{GDBN} command is @samp{info address}.
19506 @subsubheading Example
19510 @subheading The @code{-symbol-info-file} Command
19511 @findex -symbol-info-file
19513 @subsubheading Synopsis
19519 Show the file for the symbol.
19521 @subsubheading @value{GDBN} Command
19523 There's no equivalent @value{GDBN} command. @code{gdbtk} has
19524 @samp{gdb_find_file}.
19526 @subsubheading Example
19530 @subheading The @code{-symbol-info-function} Command
19531 @findex -symbol-info-function
19533 @subsubheading Synopsis
19536 -symbol-info-function
19539 Show which function the symbol lives in.
19541 @subsubheading @value{GDBN} Command
19543 @samp{gdb_get_function} in @code{gdbtk}.
19545 @subsubheading Example
19549 @subheading The @code{-symbol-info-line} Command
19550 @findex -symbol-info-line
19552 @subsubheading Synopsis
19558 Show the core addresses of the code for a source line.
19560 @subsubheading @value{GDBN} Command
19562 The corresponding @value{GDBN} command is @samp{info line}.
19563 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
19565 @subsubheading Example
19569 @subheading The @code{-symbol-info-symbol} Command
19570 @findex -symbol-info-symbol
19572 @subsubheading Synopsis
19575 -symbol-info-symbol @var{addr}
19578 Describe what symbol is at location @var{addr}.
19580 @subsubheading @value{GDBN} Command
19582 The corresponding @value{GDBN} command is @samp{info symbol}.
19584 @subsubheading Example
19588 @subheading The @code{-symbol-list-functions} Command
19589 @findex -symbol-list-functions
19591 @subsubheading Synopsis
19594 -symbol-list-functions
19597 List the functions in the executable.
19599 @subsubheading @value{GDBN} Command
19601 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
19602 @samp{gdb_search} in @code{gdbtk}.
19604 @subsubheading Example
19608 @subheading The @code{-symbol-list-lines} Command
19609 @findex -symbol-list-lines
19611 @subsubheading Synopsis
19614 -symbol-list-lines @var{filename}
19617 Print the list of lines that contain code and their associated program
19618 addresses for the given source filename. The entries are sorted in
19619 ascending PC order.
19621 @subsubheading @value{GDBN} Command
19623 There is no corresponding @value{GDBN} command.
19625 @subsubheading Example
19628 -symbol-list-lines basics.c
19629 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
19634 @subheading The @code{-symbol-list-types} Command
19635 @findex -symbol-list-types
19637 @subsubheading Synopsis
19643 List all the type names.
19645 @subsubheading @value{GDBN} Command
19647 The corresponding commands are @samp{info types} in @value{GDBN},
19648 @samp{gdb_search} in @code{gdbtk}.
19650 @subsubheading Example
19654 @subheading The @code{-symbol-list-variables} Command
19655 @findex -symbol-list-variables
19657 @subsubheading Synopsis
19660 -symbol-list-variables
19663 List all the global and static variable names.
19665 @subsubheading @value{GDBN} Command
19667 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
19669 @subsubheading Example
19673 @subheading The @code{-symbol-locate} Command
19674 @findex -symbol-locate
19676 @subsubheading Synopsis
19682 @subsubheading @value{GDBN} Command
19684 @samp{gdb_loc} in @code{gdbtk}.
19686 @subsubheading Example
19690 @subheading The @code{-symbol-type} Command
19691 @findex -symbol-type
19693 @subsubheading Synopsis
19696 -symbol-type @var{variable}
19699 Show type of @var{variable}.
19701 @subsubheading @value{GDBN} Command
19703 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
19704 @samp{gdb_obj_variable}.
19706 @subsubheading Example
19710 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19711 @node GDB/MI Target Manipulation
19712 @section @sc{gdb/mi} Target Manipulation Commands
19715 @subheading The @code{-target-attach} Command
19716 @findex -target-attach
19718 @subsubheading Synopsis
19721 -target-attach @var{pid} | @var{file}
19724 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
19726 @subsubheading @value{GDBN} command
19728 The corresponding @value{GDBN} command is @samp{attach}.
19730 @subsubheading Example
19734 @subheading The @code{-target-compare-sections} Command
19735 @findex -target-compare-sections
19737 @subsubheading Synopsis
19740 -target-compare-sections [ @var{section} ]
19743 Compare data of section @var{section} on target to the exec file.
19744 Without the argument, all sections are compared.
19746 @subsubheading @value{GDBN} Command
19748 The @value{GDBN} equivalent is @samp{compare-sections}.
19750 @subsubheading Example
19754 @subheading The @code{-target-detach} Command
19755 @findex -target-detach
19757 @subsubheading Synopsis
19763 Disconnect from the remote target. There's no output.
19765 @subsubheading @value{GDBN} command
19767 The corresponding @value{GDBN} command is @samp{detach}.
19769 @subsubheading Example
19779 @subheading The @code{-target-disconnect} Command
19780 @findex -target-disconnect
19782 @subsubheading Synopsis
19788 Disconnect from the remote target. There's no output.
19790 @subsubheading @value{GDBN} command
19792 The corresponding @value{GDBN} command is @samp{disconnect}.
19794 @subsubheading Example
19804 @subheading The @code{-target-download} Command
19805 @findex -target-download
19807 @subsubheading Synopsis
19813 Loads the executable onto the remote target.
19814 It prints out an update message every half second, which includes the fields:
19818 The name of the section.
19820 The size of what has been sent so far for that section.
19822 The size of the section.
19824 The total size of what was sent so far (the current and the previous sections).
19826 The size of the overall executable to download.
19830 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
19831 @sc{gdb/mi} Output Syntax}).
19833 In addition, it prints the name and size of the sections, as they are
19834 downloaded. These messages include the following fields:
19838 The name of the section.
19840 The size of the section.
19842 The size of the overall executable to download.
19846 At the end, a summary is printed.
19848 @subsubheading @value{GDBN} Command
19850 The corresponding @value{GDBN} command is @samp{load}.
19852 @subsubheading Example
19854 Note: each status message appears on a single line. Here the messages
19855 have been broken down so that they can fit onto a page.
19860 +download,@{section=".text",section-size="6668",total-size="9880"@}
19861 +download,@{section=".text",section-sent="512",section-size="6668",
19862 total-sent="512",total-size="9880"@}
19863 +download,@{section=".text",section-sent="1024",section-size="6668",
19864 total-sent="1024",total-size="9880"@}
19865 +download,@{section=".text",section-sent="1536",section-size="6668",
19866 total-sent="1536",total-size="9880"@}
19867 +download,@{section=".text",section-sent="2048",section-size="6668",
19868 total-sent="2048",total-size="9880"@}
19869 +download,@{section=".text",section-sent="2560",section-size="6668",
19870 total-sent="2560",total-size="9880"@}
19871 +download,@{section=".text",section-sent="3072",section-size="6668",
19872 total-sent="3072",total-size="9880"@}
19873 +download,@{section=".text",section-sent="3584",section-size="6668",
19874 total-sent="3584",total-size="9880"@}
19875 +download,@{section=".text",section-sent="4096",section-size="6668",
19876 total-sent="4096",total-size="9880"@}
19877 +download,@{section=".text",section-sent="4608",section-size="6668",
19878 total-sent="4608",total-size="9880"@}
19879 +download,@{section=".text",section-sent="5120",section-size="6668",
19880 total-sent="5120",total-size="9880"@}
19881 +download,@{section=".text",section-sent="5632",section-size="6668",
19882 total-sent="5632",total-size="9880"@}
19883 +download,@{section=".text",section-sent="6144",section-size="6668",
19884 total-sent="6144",total-size="9880"@}
19885 +download,@{section=".text",section-sent="6656",section-size="6668",
19886 total-sent="6656",total-size="9880"@}
19887 +download,@{section=".init",section-size="28",total-size="9880"@}
19888 +download,@{section=".fini",section-size="28",total-size="9880"@}
19889 +download,@{section=".data",section-size="3156",total-size="9880"@}
19890 +download,@{section=".data",section-sent="512",section-size="3156",
19891 total-sent="7236",total-size="9880"@}
19892 +download,@{section=".data",section-sent="1024",section-size="3156",
19893 total-sent="7748",total-size="9880"@}
19894 +download,@{section=".data",section-sent="1536",section-size="3156",
19895 total-sent="8260",total-size="9880"@}
19896 +download,@{section=".data",section-sent="2048",section-size="3156",
19897 total-sent="8772",total-size="9880"@}
19898 +download,@{section=".data",section-sent="2560",section-size="3156",
19899 total-sent="9284",total-size="9880"@}
19900 +download,@{section=".data",section-sent="3072",section-size="3156",
19901 total-sent="9796",total-size="9880"@}
19902 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
19908 @subheading The @code{-target-exec-status} Command
19909 @findex -target-exec-status
19911 @subsubheading Synopsis
19914 -target-exec-status
19917 Provide information on the state of the target (whether it is running or
19918 not, for instance).
19920 @subsubheading @value{GDBN} Command
19922 There's no equivalent @value{GDBN} command.
19924 @subsubheading Example
19928 @subheading The @code{-target-list-available-targets} Command
19929 @findex -target-list-available-targets
19931 @subsubheading Synopsis
19934 -target-list-available-targets
19937 List the possible targets to connect to.
19939 @subsubheading @value{GDBN} Command
19941 The corresponding @value{GDBN} command is @samp{help target}.
19943 @subsubheading Example
19947 @subheading The @code{-target-list-current-targets} Command
19948 @findex -target-list-current-targets
19950 @subsubheading Synopsis
19953 -target-list-current-targets
19956 Describe the current target.
19958 @subsubheading @value{GDBN} Command
19960 The corresponding information is printed by @samp{info file} (among
19963 @subsubheading Example
19967 @subheading The @code{-target-list-parameters} Command
19968 @findex -target-list-parameters
19970 @subsubheading Synopsis
19973 -target-list-parameters
19978 @subsubheading @value{GDBN} Command
19982 @subsubheading Example
19986 @subheading The @code{-target-select} Command
19987 @findex -target-select
19989 @subsubheading Synopsis
19992 -target-select @var{type} @var{parameters @dots{}}
19995 Connect @value{GDBN} to the remote target. This command takes two args:
19999 The type of target, for instance @samp{async}, @samp{remote}, etc.
20000 @item @var{parameters}
20001 Device names, host names and the like. @xref{Target Commands, ,
20002 Commands for managing targets}, for more details.
20005 The output is a connection notification, followed by the address at
20006 which the target program is, in the following form:
20009 ^connected,addr="@var{address}",func="@var{function name}",
20010 args=[@var{arg list}]
20013 @subsubheading @value{GDBN} Command
20015 The corresponding @value{GDBN} command is @samp{target}.
20017 @subsubheading Example
20021 -target-select async /dev/ttya
20022 ^connected,addr="0xfe00a300",func="??",args=[]
20026 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20027 @node GDB/MI Thread Commands
20028 @section @sc{gdb/mi} Thread Commands
20031 @subheading The @code{-thread-info} Command
20032 @findex -thread-info
20034 @subsubheading Synopsis
20040 @subsubheading @value{GDBN} command
20044 @subsubheading Example
20048 @subheading The @code{-thread-list-all-threads} Command
20049 @findex -thread-list-all-threads
20051 @subsubheading Synopsis
20054 -thread-list-all-threads
20057 @subsubheading @value{GDBN} Command
20059 The equivalent @value{GDBN} command is @samp{info threads}.
20061 @subsubheading Example
20065 @subheading The @code{-thread-list-ids} Command
20066 @findex -thread-list-ids
20068 @subsubheading Synopsis
20074 Produces a list of the currently known @value{GDBN} thread ids. At the
20075 end of the list it also prints the total number of such threads.
20077 @subsubheading @value{GDBN} Command
20079 Part of @samp{info threads} supplies the same information.
20081 @subsubheading Example
20083 No threads present, besides the main process:
20088 ^done,thread-ids=@{@},number-of-threads="0"
20098 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
20099 number-of-threads="3"
20104 @subheading The @code{-thread-select} Command
20105 @findex -thread-select
20107 @subsubheading Synopsis
20110 -thread-select @var{threadnum}
20113 Make @var{threadnum} the current thread. It prints the number of the new
20114 current thread, and the topmost frame for that thread.
20116 @subsubheading @value{GDBN} Command
20118 The corresponding @value{GDBN} command is @samp{thread}.
20120 @subsubheading Example
20127 *stopped,reason="end-stepping-range",thread-id="2",line="187",
20128 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
20132 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
20133 number-of-threads="3"
20136 ^done,new-thread-id="3",
20137 frame=@{level="0",func="vprintf",
20138 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
20139 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
20143 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20144 @node GDB/MI Tracepoint Commands
20145 @section @sc{gdb/mi} Tracepoint Commands
20147 The tracepoint commands are not yet implemented.
20149 @c @subheading -trace-actions
20151 @c @subheading -trace-delete
20153 @c @subheading -trace-disable
20155 @c @subheading -trace-dump
20157 @c @subheading -trace-enable
20159 @c @subheading -trace-exists
20161 @c @subheading -trace-find
20163 @c @subheading -trace-frame-number
20165 @c @subheading -trace-info
20167 @c @subheading -trace-insert
20169 @c @subheading -trace-list
20171 @c @subheading -trace-pass-count
20173 @c @subheading -trace-save
20175 @c @subheading -trace-start
20177 @c @subheading -trace-stop
20180 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20181 @node GDB/MI Variable Objects
20182 @section @sc{gdb/mi} Variable Objects
20185 @subheading Motivation for Variable Objects in @sc{gdb/mi}
20187 For the implementation of a variable debugger window (locals, watched
20188 expressions, etc.), we are proposing the adaptation of the existing code
20189 used by @code{Insight}.
20191 The two main reasons for that are:
20195 It has been proven in practice (it is already on its second generation).
20198 It will shorten development time (needless to say how important it is
20202 The original interface was designed to be used by Tcl code, so it was
20203 slightly changed so it could be used through @sc{gdb/mi}. This section
20204 describes the @sc{gdb/mi} operations that will be available and gives some
20205 hints about their use.
20207 @emph{Note}: In addition to the set of operations described here, we
20208 expect the @sc{gui} implementation of a variable window to require, at
20209 least, the following operations:
20212 @item @code{-gdb-show} @code{output-radix}
20213 @item @code{-stack-list-arguments}
20214 @item @code{-stack-list-locals}
20215 @item @code{-stack-select-frame}
20218 @subheading Introduction to Variable Objects in @sc{gdb/mi}
20220 @cindex variable objects in @sc{gdb/mi}
20221 The basic idea behind variable objects is the creation of a named object
20222 to represent a variable, an expression, a memory location or even a CPU
20223 register. For each object created, a set of operations is available for
20224 examining or changing its properties.
20226 Furthermore, complex data types, such as C structures, are represented
20227 in a tree format. For instance, the @code{struct} type variable is the
20228 root and the children will represent the struct members. If a child
20229 is itself of a complex type, it will also have children of its own.
20230 Appropriate language differences are handled for C, C@t{++} and Java.
20232 When returning the actual values of the objects, this facility allows
20233 for the individual selection of the display format used in the result
20234 creation. It can be chosen among: binary, decimal, hexadecimal, octal
20235 and natural. Natural refers to a default format automatically
20236 chosen based on the variable type (like decimal for an @code{int}, hex
20237 for pointers, etc.).
20239 The following is the complete set of @sc{gdb/mi} operations defined to
20240 access this functionality:
20242 @multitable @columnfractions .4 .6
20243 @item @strong{Operation}
20244 @tab @strong{Description}
20246 @item @code{-var-create}
20247 @tab create a variable object
20248 @item @code{-var-delete}
20249 @tab delete the variable object and its children
20250 @item @code{-var-set-format}
20251 @tab set the display format of this variable
20252 @item @code{-var-show-format}
20253 @tab show the display format of this variable
20254 @item @code{-var-info-num-children}
20255 @tab tells how many children this object has
20256 @item @code{-var-list-children}
20257 @tab return a list of the object's children
20258 @item @code{-var-info-type}
20259 @tab show the type of this variable object
20260 @item @code{-var-info-expression}
20261 @tab print what this variable object represents
20262 @item @code{-var-show-attributes}
20263 @tab is this variable editable? does it exist here?
20264 @item @code{-var-evaluate-expression}
20265 @tab get the value of this variable
20266 @item @code{-var-assign}
20267 @tab set the value of this variable
20268 @item @code{-var-update}
20269 @tab update the variable and its children
20272 In the next subsection we describe each operation in detail and suggest
20273 how it can be used.
20275 @subheading Description And Use of Operations on Variable Objects
20277 @subheading The @code{-var-create} Command
20278 @findex -var-create
20280 @subsubheading Synopsis
20283 -var-create @{@var{name} | "-"@}
20284 @{@var{frame-addr} | "*"@} @var{expression}
20287 This operation creates a variable object, which allows the monitoring of
20288 a variable, the result of an expression, a memory cell or a CPU
20291 The @var{name} parameter is the string by which the object can be
20292 referenced. It must be unique. If @samp{-} is specified, the varobj
20293 system will generate a string ``varNNNNNN'' automatically. It will be
20294 unique provided that one does not specify @var{name} on that format.
20295 The command fails if a duplicate name is found.
20297 The frame under which the expression should be evaluated can be
20298 specified by @var{frame-addr}. A @samp{*} indicates that the current
20299 frame should be used.
20301 @var{expression} is any expression valid on the current language set (must not
20302 begin with a @samp{*}), or one of the following:
20306 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
20309 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
20312 @samp{$@var{regname}} --- a CPU register name
20315 @subsubheading Result
20317 This operation returns the name, number of children and the type of the
20318 object created. Type is returned as a string as the ones generated by
20319 the @value{GDBN} CLI:
20322 name="@var{name}",numchild="N",type="@var{type}"
20326 @subheading The @code{-var-delete} Command
20327 @findex -var-delete
20329 @subsubheading Synopsis
20332 -var-delete @var{name}
20335 Deletes a previously created variable object and all of its children.
20337 Returns an error if the object @var{name} is not found.
20340 @subheading The @code{-var-set-format} Command
20341 @findex -var-set-format
20343 @subsubheading Synopsis
20346 -var-set-format @var{name} @var{format-spec}
20349 Sets the output format for the value of the object @var{name} to be
20352 The syntax for the @var{format-spec} is as follows:
20355 @var{format-spec} @expansion{}
20356 @{binary | decimal | hexadecimal | octal | natural@}
20360 @subheading The @code{-var-show-format} Command
20361 @findex -var-show-format
20363 @subsubheading Synopsis
20366 -var-show-format @var{name}
20369 Returns the format used to display the value of the object @var{name}.
20372 @var{format} @expansion{}
20377 @subheading The @code{-var-info-num-children} Command
20378 @findex -var-info-num-children
20380 @subsubheading Synopsis
20383 -var-info-num-children @var{name}
20386 Returns the number of children of a variable object @var{name}:
20393 @subheading The @code{-var-list-children} Command
20394 @findex -var-list-children
20396 @subsubheading Synopsis
20399 -var-list-children [@var{print-values}] @var{name}
20402 Returns a list of the children of the specified variable object. With
20403 just the variable object name as an argument or with an optional
20404 preceding argument of 0 or @code{--no-values}, prints only the names of the
20405 variables. With an optional preceding argument of 1 or @code{--all-values},
20406 also prints their values.
20408 @subsubheading Example
20412 -var-list-children n
20413 numchild=@var{n},children=[@{name=@var{name},
20414 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
20416 -var-list-children --all-values n
20417 numchild=@var{n},children=[@{name=@var{name},
20418 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
20422 @subheading The @code{-var-info-type} Command
20423 @findex -var-info-type
20425 @subsubheading Synopsis
20428 -var-info-type @var{name}
20431 Returns the type of the specified variable @var{name}. The type is
20432 returned as a string in the same format as it is output by the
20436 type=@var{typename}
20440 @subheading The @code{-var-info-expression} Command
20441 @findex -var-info-expression
20443 @subsubheading Synopsis
20446 -var-info-expression @var{name}
20449 Returns what is represented by the variable object @var{name}:
20452 lang=@var{lang-spec},exp=@var{expression}
20456 where @var{lang-spec} is @code{@{"C" | "C++" | "Java"@}}.
20458 @subheading The @code{-var-show-attributes} Command
20459 @findex -var-show-attributes
20461 @subsubheading Synopsis
20464 -var-show-attributes @var{name}
20467 List attributes of the specified variable object @var{name}:
20470 status=@var{attr} [ ( ,@var{attr} )* ]
20474 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
20476 @subheading The @code{-var-evaluate-expression} Command
20477 @findex -var-evaluate-expression
20479 @subsubheading Synopsis
20482 -var-evaluate-expression @var{name}
20485 Evaluates the expression that is represented by the specified variable
20486 object and returns its value as a string in the current format specified
20493 Note that one must invoke @code{-var-list-children} for a variable
20494 before the value of a child variable can be evaluated.
20496 @subheading The @code{-var-assign} Command
20497 @findex -var-assign
20499 @subsubheading Synopsis
20502 -var-assign @var{name} @var{expression}
20505 Assigns the value of @var{expression} to the variable object specified
20506 by @var{name}. The object must be @samp{editable}. If the variable's
20507 value is altered by the assign, the variable will show up in any
20508 subsequent @code{-var-update} list.
20510 @subsubheading Example
20518 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
20522 @subheading The @code{-var-update} Command
20523 @findex -var-update
20525 @subsubheading Synopsis
20528 -var-update @{@var{name} | "*"@}
20531 Update the value of the variable object @var{name} by evaluating its
20532 expression after fetching all the new values from memory or registers.
20533 A @samp{*} causes all existing variable objects to be updated.
20537 @chapter @value{GDBN} Annotations
20539 This chapter describes annotations in @value{GDBN}. Annotations were
20540 designed to interface @value{GDBN} to graphical user interfaces or other
20541 similar programs which want to interact with @value{GDBN} at a
20542 relatively high level.
20544 The annotation mechanism has largely been superseeded by @sc{gdb/mi}
20548 This is Edition @value{EDITION}, @value{DATE}.
20552 * Annotations Overview:: What annotations are; the general syntax.
20553 * Server Prefix:: Issuing a command without affecting user state.
20554 * Prompting:: Annotations marking @value{GDBN}'s need for input.
20555 * Errors:: Annotations for error messages.
20556 * Invalidation:: Some annotations describe things now invalid.
20557 * Annotations for Running::
20558 Whether the program is running, how it stopped, etc.
20559 * Source Annotations:: Annotations describing source code.
20562 @node Annotations Overview
20563 @section What is an Annotation?
20564 @cindex annotations
20566 Annotations start with a newline character, two @samp{control-z}
20567 characters, and the name of the annotation. If there is no additional
20568 information associated with this annotation, the name of the annotation
20569 is followed immediately by a newline. If there is additional
20570 information, the name of the annotation is followed by a space, the
20571 additional information, and a newline. The additional information
20572 cannot contain newline characters.
20574 Any output not beginning with a newline and two @samp{control-z}
20575 characters denotes literal output from @value{GDBN}. Currently there is
20576 no need for @value{GDBN} to output a newline followed by two
20577 @samp{control-z} characters, but if there was such a need, the
20578 annotations could be extended with an @samp{escape} annotation which
20579 means those three characters as output.
20581 The annotation @var{level}, which is specified using the
20582 @option{--annotate} command line option (@pxref{Mode Options}), controls
20583 how much information @value{GDBN} prints together with its prompt,
20584 values of expressions, source lines, and other types of output. Level 0
20585 is for no anntations, level 1 is for use when @value{GDBN} is run as a
20586 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
20587 for programs that control @value{GDBN}, and level 2 annotations have
20588 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
20589 Interface, annotate, GDB's Obsolete Annotations}).
20592 @kindex set annotate
20593 @item set annotate @var{level}
20594 The @value{GDBN} command @code{set annotate} sets the level of
20595 annotations to the specified @var{level}.
20597 @item show annotate
20598 @kindex show annotate
20599 Show the current annotation level.
20602 This chapter describes level 3 annotations.
20604 A simple example of starting up @value{GDBN} with annotations is:
20607 $ @kbd{gdb --annotate=3}
20609 Copyright 2003 Free Software Foundation, Inc.
20610 GDB is free software, covered by the GNU General Public License,
20611 and you are welcome to change it and/or distribute copies of it
20612 under certain conditions.
20613 Type "show copying" to see the conditions.
20614 There is absolutely no warranty for GDB. Type "show warranty"
20616 This GDB was configured as "i386-pc-linux-gnu"
20627 Here @samp{quit} is input to @value{GDBN}; the rest is output from
20628 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
20629 denotes a @samp{control-z} character) are annotations; the rest is
20630 output from @value{GDBN}.
20632 @node Server Prefix
20633 @section The Server Prefix
20634 @cindex server prefix for annotations
20636 To issue a command to @value{GDBN} without affecting certain aspects of
20637 the state which is seen by users, prefix it with @samp{server }. This
20638 means that this command will not affect the command history, nor will it
20639 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
20640 pressed on a line by itself.
20642 The server prefix does not affect the recording of values into the value
20643 history; to print a value without recording it into the value history,
20644 use the @code{output} command instead of the @code{print} command.
20647 @section Annotation for @value{GDBN} Input
20649 @cindex annotations for prompts
20650 When @value{GDBN} prompts for input, it annotates this fact so it is possible
20651 to know when to send output, when the output from a given command is
20654 Different kinds of input each have a different @dfn{input type}. Each
20655 input type has three annotations: a @code{pre-} annotation, which
20656 denotes the beginning of any prompt which is being output, a plain
20657 annotation, which denotes the end of the prompt, and then a @code{post-}
20658 annotation which denotes the end of any echo which may (or may not) be
20659 associated with the input. For example, the @code{prompt} input type
20660 features the following annotations:
20668 The input types are
20673 @findex post-prompt
20675 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
20677 @findex pre-commands
20679 @findex post-commands
20681 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
20682 command. The annotations are repeated for each command which is input.
20684 @findex pre-overload-choice
20685 @findex overload-choice
20686 @findex post-overload-choice
20687 @item overload-choice
20688 When @value{GDBN} wants the user to select between various overloaded functions.
20694 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
20696 @findex pre-prompt-for-continue
20697 @findex prompt-for-continue
20698 @findex post-prompt-for-continue
20699 @item prompt-for-continue
20700 When @value{GDBN} is asking the user to press return to continue. Note: Don't
20701 expect this to work well; instead use @code{set height 0} to disable
20702 prompting. This is because the counting of lines is buggy in the
20703 presence of annotations.
20708 @cindex annotations for errors, warnings and interrupts
20715 This annotation occurs right before @value{GDBN} responds to an interrupt.
20722 This annotation occurs right before @value{GDBN} responds to an error.
20724 Quit and error annotations indicate that any annotations which @value{GDBN} was
20725 in the middle of may end abruptly. For example, if a
20726 @code{value-history-begin} annotation is followed by a @code{error}, one
20727 cannot expect to receive the matching @code{value-history-end}. One
20728 cannot expect not to receive it either, however; an error annotation
20729 does not necessarily mean that @value{GDBN} is immediately returning all the way
20732 @findex error-begin
20733 A quit or error annotation may be preceded by
20739 Any output between that and the quit or error annotation is the error
20742 Warning messages are not yet annotated.
20743 @c If we want to change that, need to fix warning(), type_error(),
20744 @c range_error(), and possibly other places.
20747 @section Invalidation Notices
20749 @cindex annotations for invalidation messages
20750 The following annotations say that certain pieces of state may have
20754 @findex frames-invalid
20755 @item ^Z^Zframes-invalid
20757 The frames (for example, output from the @code{backtrace} command) may
20760 @findex breakpoints-invalid
20761 @item ^Z^Zbreakpoints-invalid
20763 The breakpoints may have changed. For example, the user just added or
20764 deleted a breakpoint.
20767 @node Annotations for Running
20768 @section Running the Program
20769 @cindex annotations for running programs
20773 When the program starts executing due to a @value{GDBN} command such as
20774 @code{step} or @code{continue},
20780 is output. When the program stops,
20786 is output. Before the @code{stopped} annotation, a variety of
20787 annotations describe how the program stopped.
20791 @item ^Z^Zexited @var{exit-status}
20792 The program exited, and @var{exit-status} is the exit status (zero for
20793 successful exit, otherwise nonzero).
20796 @findex signal-name
20797 @findex signal-name-end
20798 @findex signal-string
20799 @findex signal-string-end
20800 @item ^Z^Zsignalled
20801 The program exited with a signal. After the @code{^Z^Zsignalled}, the
20802 annotation continues:
20808 ^Z^Zsignal-name-end
20812 ^Z^Zsignal-string-end
20817 where @var{name} is the name of the signal, such as @code{SIGILL} or
20818 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
20819 as @code{Illegal Instruction} or @code{Segmentation fault}.
20820 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
20821 user's benefit and have no particular format.
20825 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
20826 just saying that the program received the signal, not that it was
20827 terminated with it.
20830 @item ^Z^Zbreakpoint @var{number}
20831 The program hit breakpoint number @var{number}.
20834 @item ^Z^Zwatchpoint @var{number}
20835 The program hit watchpoint number @var{number}.
20838 @node Source Annotations
20839 @section Displaying Source
20840 @cindex annotations for source display
20843 The following annotation is used instead of displaying source code:
20846 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
20849 where @var{filename} is an absolute file name indicating which source
20850 file, @var{line} is the line number within that file (where 1 is the
20851 first line in the file), @var{character} is the character position
20852 within the file (where 0 is the first character in the file) (for most
20853 debug formats this will necessarily point to the beginning of a line),
20854 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
20855 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
20856 @var{addr} is the address in the target program associated with the
20857 source which is being displayed. @var{addr} is in the form @samp{0x}
20858 followed by one or more lowercase hex digits (note that this does not
20859 depend on the language).
20862 @chapter Reporting Bugs in @value{GDBN}
20863 @cindex bugs in @value{GDBN}
20864 @cindex reporting bugs in @value{GDBN}
20866 Your bug reports play an essential role in making @value{GDBN} reliable.
20868 Reporting a bug may help you by bringing a solution to your problem, or it
20869 may not. But in any case the principal function of a bug report is to help
20870 the entire community by making the next version of @value{GDBN} work better. Bug
20871 reports are your contribution to the maintenance of @value{GDBN}.
20873 In order for a bug report to serve its purpose, you must include the
20874 information that enables us to fix the bug.
20877 * Bug Criteria:: Have you found a bug?
20878 * Bug Reporting:: How to report bugs
20882 @section Have you found a bug?
20883 @cindex bug criteria
20885 If you are not sure whether you have found a bug, here are some guidelines:
20888 @cindex fatal signal
20889 @cindex debugger crash
20890 @cindex crash of debugger
20892 If the debugger gets a fatal signal, for any input whatever, that is a
20893 @value{GDBN} bug. Reliable debuggers never crash.
20895 @cindex error on valid input
20897 If @value{GDBN} produces an error message for valid input, that is a
20898 bug. (Note that if you're cross debugging, the problem may also be
20899 somewhere in the connection to the target.)
20901 @cindex invalid input
20903 If @value{GDBN} does not produce an error message for invalid input,
20904 that is a bug. However, you should note that your idea of
20905 ``invalid input'' might be our idea of ``an extension'' or ``support
20906 for traditional practice''.
20909 If you are an experienced user of debugging tools, your suggestions
20910 for improvement of @value{GDBN} are welcome in any case.
20913 @node Bug Reporting
20914 @section How to report bugs
20915 @cindex bug reports
20916 @cindex @value{GDBN} bugs, reporting
20918 A number of companies and individuals offer support for @sc{gnu} products.
20919 If you obtained @value{GDBN} from a support organization, we recommend you
20920 contact that organization first.
20922 You can find contact information for many support companies and
20923 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
20925 @c should add a web page ref...
20927 In any event, we also recommend that you submit bug reports for
20928 @value{GDBN}. The prefered method is to submit them directly using
20929 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
20930 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
20933 @strong{Do not send bug reports to @samp{info-gdb}, or to
20934 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
20935 not want to receive bug reports. Those that do have arranged to receive
20938 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
20939 serves as a repeater. The mailing list and the newsgroup carry exactly
20940 the same messages. Often people think of posting bug reports to the
20941 newsgroup instead of mailing them. This appears to work, but it has one
20942 problem which can be crucial: a newsgroup posting often lacks a mail
20943 path back to the sender. Thus, if we need to ask for more information,
20944 we may be unable to reach you. For this reason, it is better to send
20945 bug reports to the mailing list.
20947 The fundamental principle of reporting bugs usefully is this:
20948 @strong{report all the facts}. If you are not sure whether to state a
20949 fact or leave it out, state it!
20951 Often people omit facts because they think they know what causes the
20952 problem and assume that some details do not matter. Thus, you might
20953 assume that the name of the variable you use in an example does not matter.
20954 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
20955 stray memory reference which happens to fetch from the location where that
20956 name is stored in memory; perhaps, if the name were different, the contents
20957 of that location would fool the debugger into doing the right thing despite
20958 the bug. Play it safe and give a specific, complete example. That is the
20959 easiest thing for you to do, and the most helpful.
20961 Keep in mind that the purpose of a bug report is to enable us to fix the
20962 bug. It may be that the bug has been reported previously, but neither
20963 you nor we can know that unless your bug report is complete and
20966 Sometimes people give a few sketchy facts and ask, ``Does this ring a
20967 bell?'' Those bug reports are useless, and we urge everyone to
20968 @emph{refuse to respond to them} except to chide the sender to report
20971 To enable us to fix the bug, you should include all these things:
20975 The version of @value{GDBN}. @value{GDBN} announces it if you start
20976 with no arguments; you can also print it at any time using @code{show
20979 Without this, we will not know whether there is any point in looking for
20980 the bug in the current version of @value{GDBN}.
20983 The type of machine you are using, and the operating system name and
20987 What compiler (and its version) was used to compile @value{GDBN}---e.g.
20988 ``@value{GCC}--2.8.1''.
20991 What compiler (and its version) was used to compile the program you are
20992 debugging---e.g. ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
20993 C Compiler''. For GCC, you can say @code{gcc --version} to get this
20994 information; for other compilers, see the documentation for those
20998 The command arguments you gave the compiler to compile your example and
20999 observe the bug. For example, did you use @samp{-O}? To guarantee
21000 you will not omit something important, list them all. A copy of the
21001 Makefile (or the output from make) is sufficient.
21003 If we were to try to guess the arguments, we would probably guess wrong
21004 and then we might not encounter the bug.
21007 A complete input script, and all necessary source files, that will
21011 A description of what behavior you observe that you believe is
21012 incorrect. For example, ``It gets a fatal signal.''
21014 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
21015 will certainly notice it. But if the bug is incorrect output, we might
21016 not notice unless it is glaringly wrong. You might as well not give us
21017 a chance to make a mistake.
21019 Even if the problem you experience is a fatal signal, you should still
21020 say so explicitly. Suppose something strange is going on, such as, your
21021 copy of @value{GDBN} is out of synch, or you have encountered a bug in
21022 the C library on your system. (This has happened!) Your copy might
21023 crash and ours would not. If you told us to expect a crash, then when
21024 ours fails to crash, we would know that the bug was not happening for
21025 us. If you had not told us to expect a crash, then we would not be able
21026 to draw any conclusion from our observations.
21029 @cindex recording a session script
21030 To collect all this information, you can use a session recording program
21031 such as @command{script}, which is available on many Unix systems.
21032 Just run your @value{GDBN} session inside @command{script} and then
21033 include the @file{typescript} file with your bug report.
21035 Another way to record a @value{GDBN} session is to run @value{GDBN}
21036 inside Emacs and then save the entire buffer to a file.
21039 If you wish to suggest changes to the @value{GDBN} source, send us context
21040 diffs. If you even discuss something in the @value{GDBN} source, refer to
21041 it by context, not by line number.
21043 The line numbers in our development sources will not match those in your
21044 sources. Your line numbers would convey no useful information to us.
21048 Here are some things that are not necessary:
21052 A description of the envelope of the bug.
21054 Often people who encounter a bug spend a lot of time investigating
21055 which changes to the input file will make the bug go away and which
21056 changes will not affect it.
21058 This is often time consuming and not very useful, because the way we
21059 will find the bug is by running a single example under the debugger
21060 with breakpoints, not by pure deduction from a series of examples.
21061 We recommend that you save your time for something else.
21063 Of course, if you can find a simpler example to report @emph{instead}
21064 of the original one, that is a convenience for us. Errors in the
21065 output will be easier to spot, running under the debugger will take
21066 less time, and so on.
21068 However, simplification is not vital; if you do not want to do this,
21069 report the bug anyway and send us the entire test case you used.
21072 A patch for the bug.
21074 A patch for the bug does help us if it is a good one. But do not omit
21075 the necessary information, such as the test case, on the assumption that
21076 a patch is all we need. We might see problems with your patch and decide
21077 to fix the problem another way, or we might not understand it at all.
21079 Sometimes with a program as complicated as @value{GDBN} it is very hard to
21080 construct an example that will make the program follow a certain path
21081 through the code. If you do not send us the example, we will not be able
21082 to construct one, so we will not be able to verify that the bug is fixed.
21084 And if we cannot understand what bug you are trying to fix, or why your
21085 patch should be an improvement, we will not install it. A test case will
21086 help us to understand.
21089 A guess about what the bug is or what it depends on.
21091 Such guesses are usually wrong. Even we cannot guess right about such
21092 things without first using the debugger to find the facts.
21095 @c The readline documentation is distributed with the readline code
21096 @c and consists of the two following files:
21098 @c inc-hist.texinfo
21099 @c Use -I with makeinfo to point to the appropriate directory,
21100 @c environment var TEXINPUTS with TeX.
21101 @include rluser.texinfo
21102 @include inc-hist.texinfo
21105 @node Formatting Documentation
21106 @appendix Formatting Documentation
21108 @cindex @value{GDBN} reference card
21109 @cindex reference card
21110 The @value{GDBN} 4 release includes an already-formatted reference card, ready
21111 for printing with PostScript or Ghostscript, in the @file{gdb}
21112 subdirectory of the main source directory@footnote{In
21113 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
21114 release.}. If you can use PostScript or Ghostscript with your printer,
21115 you can print the reference card immediately with @file{refcard.ps}.
21117 The release also includes the source for the reference card. You
21118 can format it, using @TeX{}, by typing:
21124 The @value{GDBN} reference card is designed to print in @dfn{landscape}
21125 mode on US ``letter'' size paper;
21126 that is, on a sheet 11 inches wide by 8.5 inches
21127 high. You will need to specify this form of printing as an option to
21128 your @sc{dvi} output program.
21130 @cindex documentation
21132 All the documentation for @value{GDBN} comes as part of the machine-readable
21133 distribution. The documentation is written in Texinfo format, which is
21134 a documentation system that uses a single source file to produce both
21135 on-line information and a printed manual. You can use one of the Info
21136 formatting commands to create the on-line version of the documentation
21137 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
21139 @value{GDBN} includes an already formatted copy of the on-line Info
21140 version of this manual in the @file{gdb} subdirectory. The main Info
21141 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
21142 subordinate files matching @samp{gdb.info*} in the same directory. If
21143 necessary, you can print out these files, or read them with any editor;
21144 but they are easier to read using the @code{info} subsystem in @sc{gnu}
21145 Emacs or the standalone @code{info} program, available as part of the
21146 @sc{gnu} Texinfo distribution.
21148 If you want to format these Info files yourself, you need one of the
21149 Info formatting programs, such as @code{texinfo-format-buffer} or
21152 If you have @code{makeinfo} installed, and are in the top level
21153 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
21154 version @value{GDBVN}), you can make the Info file by typing:
21161 If you want to typeset and print copies of this manual, you need @TeX{},
21162 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
21163 Texinfo definitions file.
21165 @TeX{} is a typesetting program; it does not print files directly, but
21166 produces output files called @sc{dvi} files. To print a typeset
21167 document, you need a program to print @sc{dvi} files. If your system
21168 has @TeX{} installed, chances are it has such a program. The precise
21169 command to use depends on your system; @kbd{lpr -d} is common; another
21170 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
21171 require a file name without any extension or a @samp{.dvi} extension.
21173 @TeX{} also requires a macro definitions file called
21174 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
21175 written in Texinfo format. On its own, @TeX{} cannot either read or
21176 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
21177 and is located in the @file{gdb-@var{version-number}/texinfo}
21180 If you have @TeX{} and a @sc{dvi} printer program installed, you can
21181 typeset and print this manual. First switch to the the @file{gdb}
21182 subdirectory of the main source directory (for example, to
21183 @file{gdb-@value{GDBVN}/gdb}) and type:
21189 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
21191 @node Installing GDB
21192 @appendix Installing @value{GDBN}
21193 @cindex configuring @value{GDBN}
21194 @cindex installation
21195 @cindex configuring @value{GDBN}, and source tree subdirectories
21197 @value{GDBN} comes with a @code{configure} script that automates the process
21198 of preparing @value{GDBN} for installation; you can then use @code{make} to
21199 build the @code{gdb} program.
21201 @c irrelevant in info file; it's as current as the code it lives with.
21202 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
21203 look at the @file{README} file in the sources; we may have improved the
21204 installation procedures since publishing this manual.}
21207 The @value{GDBN} distribution includes all the source code you need for
21208 @value{GDBN} in a single directory, whose name is usually composed by
21209 appending the version number to @samp{gdb}.
21211 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
21212 @file{gdb-@value{GDBVN}} directory. That directory contains:
21215 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
21216 script for configuring @value{GDBN} and all its supporting libraries
21218 @item gdb-@value{GDBVN}/gdb
21219 the source specific to @value{GDBN} itself
21221 @item gdb-@value{GDBVN}/bfd
21222 source for the Binary File Descriptor library
21224 @item gdb-@value{GDBVN}/include
21225 @sc{gnu} include files
21227 @item gdb-@value{GDBVN}/libiberty
21228 source for the @samp{-liberty} free software library
21230 @item gdb-@value{GDBVN}/opcodes
21231 source for the library of opcode tables and disassemblers
21233 @item gdb-@value{GDBVN}/readline
21234 source for the @sc{gnu} command-line interface
21236 @item gdb-@value{GDBVN}/glob
21237 source for the @sc{gnu} filename pattern-matching subroutine
21239 @item gdb-@value{GDBVN}/mmalloc
21240 source for the @sc{gnu} memory-mapped malloc package
21243 The simplest way to configure and build @value{GDBN} is to run @code{configure}
21244 from the @file{gdb-@var{version-number}} source directory, which in
21245 this example is the @file{gdb-@value{GDBVN}} directory.
21247 First switch to the @file{gdb-@var{version-number}} source directory
21248 if you are not already in it; then run @code{configure}. Pass the
21249 identifier for the platform on which @value{GDBN} will run as an
21255 cd gdb-@value{GDBVN}
21256 ./configure @var{host}
21261 where @var{host} is an identifier such as @samp{sun4} or
21262 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
21263 (You can often leave off @var{host}; @code{configure} tries to guess the
21264 correct value by examining your system.)
21266 Running @samp{configure @var{host}} and then running @code{make} builds the
21267 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
21268 libraries, then @code{gdb} itself. The configured source files, and the
21269 binaries, are left in the corresponding source directories.
21272 @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
21273 system does not recognize this automatically when you run a different
21274 shell, you may need to run @code{sh} on it explicitly:
21277 sh configure @var{host}
21280 If you run @code{configure} from a directory that contains source
21281 directories for multiple libraries or programs, such as the
21282 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure}
21283 creates configuration files for every directory level underneath (unless
21284 you tell it not to, with the @samp{--norecursion} option).
21286 You should run the @code{configure} script from the top directory in the
21287 source tree, the @file{gdb-@var{version-number}} directory. If you run
21288 @code{configure} from one of the subdirectories, you will configure only
21289 that subdirectory. That is usually not what you want. In particular,
21290 if you run the first @code{configure} from the @file{gdb} subdirectory
21291 of the @file{gdb-@var{version-number}} directory, you will omit the
21292 configuration of @file{bfd}, @file{readline}, and other sibling
21293 directories of the @file{gdb} subdirectory. This leads to build errors
21294 about missing include files such as @file{bfd/bfd.h}.
21296 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
21297 However, you should make sure that the shell on your path (named by
21298 the @samp{SHELL} environment variable) is publicly readable. Remember
21299 that @value{GDBN} uses the shell to start your program---some systems refuse to
21300 let @value{GDBN} debug child processes whose programs are not readable.
21303 * Separate Objdir:: Compiling @value{GDBN} in another directory
21304 * Config Names:: Specifying names for hosts and targets
21305 * Configure Options:: Summary of options for configure
21308 @node Separate Objdir
21309 @section Compiling @value{GDBN} in another directory
21311 If you want to run @value{GDBN} versions for several host or target machines,
21312 you need a different @code{gdb} compiled for each combination of
21313 host and target. @code{configure} is designed to make this easy by
21314 allowing you to generate each configuration in a separate subdirectory,
21315 rather than in the source directory. If your @code{make} program
21316 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
21317 @code{make} in each of these directories builds the @code{gdb}
21318 program specified there.
21320 To build @code{gdb} in a separate directory, run @code{configure}
21321 with the @samp{--srcdir} option to specify where to find the source.
21322 (You also need to specify a path to find @code{configure}
21323 itself from your working directory. If the path to @code{configure}
21324 would be the same as the argument to @samp{--srcdir}, you can leave out
21325 the @samp{--srcdir} option; it is assumed.)
21327 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
21328 separate directory for a Sun 4 like this:
21332 cd gdb-@value{GDBVN}
21335 ../gdb-@value{GDBVN}/configure sun4
21340 When @code{configure} builds a configuration using a remote source
21341 directory, it creates a tree for the binaries with the same structure
21342 (and using the same names) as the tree under the source directory. In
21343 the example, you'd find the Sun 4 library @file{libiberty.a} in the
21344 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
21345 @file{gdb-sun4/gdb}.
21347 Make sure that your path to the @file{configure} script has just one
21348 instance of @file{gdb} in it. If your path to @file{configure} looks
21349 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
21350 one subdirectory of @value{GDBN}, not the whole package. This leads to
21351 build errors about missing include files such as @file{bfd/bfd.h}.
21353 One popular reason to build several @value{GDBN} configurations in separate
21354 directories is to configure @value{GDBN} for cross-compiling (where
21355 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
21356 programs that run on another machine---the @dfn{target}).
21357 You specify a cross-debugging target by
21358 giving the @samp{--target=@var{target}} option to @code{configure}.
21360 When you run @code{make} to build a program or library, you must run
21361 it in a configured directory---whatever directory you were in when you
21362 called @code{configure} (or one of its subdirectories).
21364 The @code{Makefile} that @code{configure} generates in each source
21365 directory also runs recursively. If you type @code{make} in a source
21366 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
21367 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
21368 will build all the required libraries, and then build GDB.
21370 When you have multiple hosts or targets configured in separate
21371 directories, you can run @code{make} on them in parallel (for example,
21372 if they are NFS-mounted on each of the hosts); they will not interfere
21376 @section Specifying names for hosts and targets
21378 The specifications used for hosts and targets in the @code{configure}
21379 script are based on a three-part naming scheme, but some short predefined
21380 aliases are also supported. The full naming scheme encodes three pieces
21381 of information in the following pattern:
21384 @var{architecture}-@var{vendor}-@var{os}
21387 For example, you can use the alias @code{sun4} as a @var{host} argument,
21388 or as the value for @var{target} in a @code{--target=@var{target}}
21389 option. The equivalent full name is @samp{sparc-sun-sunos4}.
21391 The @code{configure} script accompanying @value{GDBN} does not provide
21392 any query facility to list all supported host and target names or
21393 aliases. @code{configure} calls the Bourne shell script
21394 @code{config.sub} to map abbreviations to full names; you can read the
21395 script, if you wish, or you can use it to test your guesses on
21396 abbreviations---for example:
21399 % sh config.sub i386-linux
21401 % sh config.sub alpha-linux
21402 alpha-unknown-linux-gnu
21403 % sh config.sub hp9k700
21405 % sh config.sub sun4
21406 sparc-sun-sunos4.1.1
21407 % sh config.sub sun3
21408 m68k-sun-sunos4.1.1
21409 % sh config.sub i986v
21410 Invalid configuration `i986v': machine `i986v' not recognized
21414 @code{config.sub} is also distributed in the @value{GDBN} source
21415 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
21417 @node Configure Options
21418 @section @code{configure} options
21420 Here is a summary of the @code{configure} options and arguments that
21421 are most often useful for building @value{GDBN}. @code{configure} also has
21422 several other options not listed here. @inforef{What Configure
21423 Does,,configure.info}, for a full explanation of @code{configure}.
21426 configure @r{[}--help@r{]}
21427 @r{[}--prefix=@var{dir}@r{]}
21428 @r{[}--exec-prefix=@var{dir}@r{]}
21429 @r{[}--srcdir=@var{dirname}@r{]}
21430 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
21431 @r{[}--target=@var{target}@r{]}
21436 You may introduce options with a single @samp{-} rather than
21437 @samp{--} if you prefer; but you may abbreviate option names if you use
21442 Display a quick summary of how to invoke @code{configure}.
21444 @item --prefix=@var{dir}
21445 Configure the source to install programs and files under directory
21448 @item --exec-prefix=@var{dir}
21449 Configure the source to install programs under directory
21452 @c avoid splitting the warning from the explanation:
21454 @item --srcdir=@var{dirname}
21455 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
21456 @code{make} that implements the @code{VPATH} feature.}@*
21457 Use this option to make configurations in directories separate from the
21458 @value{GDBN} source directories. Among other things, you can use this to
21459 build (or maintain) several configurations simultaneously, in separate
21460 directories. @code{configure} writes configuration specific files in
21461 the current directory, but arranges for them to use the source in the
21462 directory @var{dirname}. @code{configure} creates directories under
21463 the working directory in parallel to the source directories below
21466 @item --norecursion
21467 Configure only the directory level where @code{configure} is executed; do not
21468 propagate configuration to subdirectories.
21470 @item --target=@var{target}
21471 Configure @value{GDBN} for cross-debugging programs running on the specified
21472 @var{target}. Without this option, @value{GDBN} is configured to debug
21473 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
21475 There is no convenient way to generate a list of all available targets.
21477 @item @var{host} @dots{}
21478 Configure @value{GDBN} to run on the specified @var{host}.
21480 There is no convenient way to generate a list of all available hosts.
21483 There are many other options available as well, but they are generally
21484 needed for special purposes only.
21486 @node Maintenance Commands
21487 @appendix Maintenance Commands
21488 @cindex maintenance commands
21489 @cindex internal commands
21491 In addition to commands intended for @value{GDBN} users, @value{GDBN}
21492 includes a number of commands intended for @value{GDBN} developers,
21493 that are not documented elsewhere in this manual. These commands are
21494 provided here for reference. (For commands that turn on debugging
21495 messages, see @ref{Debugging Output}.)
21498 @kindex maint agent
21499 @item maint agent @var{expression}
21500 Translate the given @var{expression} into remote agent bytecodes.
21501 This command is useful for debugging the Agent Expression mechanism
21502 (@pxref{Agent Expressions}).
21504 @kindex maint info breakpoints
21505 @item @anchor{maint info breakpoints}maint info breakpoints
21506 Using the same format as @samp{info breakpoints}, display both the
21507 breakpoints you've set explicitly, and those @value{GDBN} is using for
21508 internal purposes. Internal breakpoints are shown with negative
21509 breakpoint numbers. The type column identifies what kind of breakpoint
21514 Normal, explicitly set breakpoint.
21517 Normal, explicitly set watchpoint.
21520 Internal breakpoint, used to handle correctly stepping through
21521 @code{longjmp} calls.
21523 @item longjmp resume
21524 Internal breakpoint at the target of a @code{longjmp}.
21527 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
21530 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
21533 Shared library events.
21537 @kindex maint check-symtabs
21538 @item maint check-symtabs
21539 Check the consistency of psymtabs and symtabs.
21541 @kindex maint cplus first_component
21542 @item maint cplus first_component @var{name}
21543 Print the first C@t{++} class/namespace component of @var{name}.
21545 @kindex maint cplus namespace
21546 @item maint cplus namespace
21547 Print the list of possible C@t{++} namespaces.
21549 @kindex maint demangle
21550 @item maint demangle @var{name}
21551 Demangle a C@t{++} or Objective-C manled @var{name}.
21553 @kindex maint deprecate
21554 @kindex maint undeprecate
21555 @cindex deprecated commands
21556 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
21557 @itemx maint undeprecate @var{command}
21558 Deprecate or undeprecate the named @var{command}. Deprecated commands
21559 cause @value{GDBN} to issue a warning when you use them. The optional
21560 argument @var{replacement} says which newer command should be used in
21561 favor of the deprecated one; if it is given, @value{GDBN} will mention
21562 the replacement as part of the warning.
21564 @kindex maint dump-me
21565 @item maint dump-me
21566 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
21567 Cause a fatal signal in the debugger and force it to dump its core.
21568 This is supported only on systems which support aborting a program
21569 with the @code{SIGQUIT} signal.
21571 @kindex maint internal-error
21572 @kindex maint internal-warning
21573 @item maint internal-error @r{[}@var{message-text}@r{]}
21574 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
21575 Cause @value{GDBN} to call the internal function @code{internal_error}
21576 or @code{internal_warning} and hence behave as though an internal error
21577 or internal warning has been detected. In addition to reporting the
21578 internal problem, these functions give the user the opportunity to
21579 either quit @value{GDBN} or create a core file of the current
21580 @value{GDBN} session.
21582 These commands take an optional parameter @var{message-text} that is
21583 used as the text of the error or warning message.
21585 Here's an example of using @code{indernal-error}:
21588 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
21589 @dots{}/maint.c:121: internal-error: testing, 1, 2
21590 A problem internal to GDB has been detected. Further
21591 debugging may prove unreliable.
21592 Quit this debugging session? (y or n) @kbd{n}
21593 Create a core file? (y or n) @kbd{n}
21597 @kindex maint packet
21598 @item maint packet @var{text}
21599 If @value{GDBN} is talking to an inferior via the serial protocol,
21600 then this command sends the string @var{text} to the inferior, and
21601 displays the response packet. @value{GDBN} supplies the initial
21602 @samp{$} character, the terminating @samp{#} character, and the
21605 @kindex maint print architecture
21606 @item maint print architecture @r{[}@var{file}@r{]}
21607 Print the entire architecture configuration. The optional argument
21608 @var{file} names the file where the output goes.
21610 @kindex maint print dummy-frames
21611 @item maint print dummy-frames
21612 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
21615 (@value{GDBP}) @kbd{b add}
21617 (@value{GDBP}) @kbd{print add(2,3)}
21618 Breakpoint 2, add (a=2, b=3) at @dots{}
21620 The program being debugged stopped while in a function called from GDB.
21622 (@value{GDBP}) @kbd{maint print dummy-frames}
21623 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
21624 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
21625 call_lo=0x01014000 call_hi=0x01014001
21629 Takes an optional file parameter.
21631 @kindex maint print registers
21632 @kindex maint print raw-registers
21633 @kindex maint print cooked-registers
21634 @kindex maint print register-groups
21635 @item maint print registers @r{[}@var{file}@r{]}
21636 @itemx maint print raw-registers @r{[}@var{file}@r{]}
21637 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
21638 @itemx maint print register-groups @r{[}@var{file}@r{]}
21639 Print @value{GDBN}'s internal register data structures.
21641 The command @code{maint print raw-registers} includes the contents of
21642 the raw register cache; the command @code{maint print cooked-registers}
21643 includes the (cooked) value of all registers; and the command
21644 @code{maint print register-groups} includes the groups that each
21645 register is a member of. @xref{Registers,, Registers, gdbint,
21646 @value{GDBN} Internals}.
21648 These commands take an optional parameter, a file name to which to
21649 write the information.
21651 @kindex maint print reggroups
21652 @item maint print reggroups @r{[}@var{file}@r{]}
21653 Print @value{GDBN}'s internal register group data structures. The
21654 optional argument @var{file} tells to what file to write the
21657 The register groups info looks like this:
21660 (@value{GDBP}) @kbd{maint print reggroups}
21673 This command forces @value{GDBN} to flush its internal register cache.
21675 @kindex maint print objfiles
21676 @cindex info for known object files
21677 @item maint print objfiles
21678 Print a dump of all known object files. For each object file, this
21679 command prints its name, address in memory, and all of its psymtabs
21682 @kindex maint print statistics
21683 @cindex bcache statistics
21684 @item maint print statistics
21685 This command prints, for each object file in the program, various data
21686 about that object file followed by the byte cache (@dfn{bcache})
21687 statistics for the object file. The objfile data includes the number
21688 of minimal, partical, full, and stabs symbols, the number of types
21689 defined by the objfile, the number of as yet unexpanded psym tables,
21690 the number of line tables and string tables, and the amount of memory
21691 used by the various tables. The bcache statistics include the counts,
21692 sizes, and counts of duplicates of all and unique objects, max,
21693 average, and median entry size, total memory used and its overhead and
21694 savings, and various measures of the hash table size and chain
21697 @kindex maint print type
21698 @cindex type chain of a data type
21699 @item maint print type @var{expr}
21700 Print the type chain for a type specified by @var{expr}. The argument
21701 can be either a type name or a symbol. If it is a symbol, the type of
21702 that symbol is described. The type chain produced by this command is
21703 a recursive definition of the data type as stored in @value{GDBN}'s
21704 data structures, including its flags and contained types.
21706 @kindex maint set dwarf2 max-cache-age
21707 @kindex maint show dwarf2 max-cache-age
21708 @item maint set dwarf2 max-cache-age
21709 @itemx maint show dwarf2 max-cache-age
21710 Control the DWARF 2 compilation unit cache.
21712 @cindex DWARF 2 compilation units cache
21713 In object files with inter-compilation-unit references, such as those
21714 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
21715 reader needs to frequently refer to previously read compilation units.
21716 This setting controls how long a compilation unit will remain in the
21717 cache if it is not referenced. A higher limit means that cached
21718 compilation units will be stored in memory longer, and more total
21719 memory will be used. Setting it to zero disables caching, which will
21720 slow down @value{GDBN} startup, but reduce memory consumption.
21722 @kindex maint set profile
21723 @kindex maint show profile
21724 @cindex profiling GDB
21725 @item maint set profile
21726 @itemx maint show profile
21727 Control profiling of @value{GDBN}.
21729 Profiling will be disabled until you use the @samp{maint set profile}
21730 command to enable it. When you enable profiling, the system will begin
21731 collecting timing and execution count data; when you disable profiling or
21732 exit @value{GDBN}, the results will be written to a log file. Remember that
21733 if you use profiling, @value{GDBN} will overwrite the profiling log file
21734 (often called @file{gmon.out}). If you have a record of important profiling
21735 data in a @file{gmon.out} file, be sure to move it to a safe location.
21737 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
21738 compiled with the @samp{-pg} compiler option.
21740 @kindex maint show-debug-regs
21741 @cindex x86 hardware debug registers
21742 @item maint show-debug-regs
21743 Control whether to show variables that mirror the x86 hardware debug
21744 registers. Use @code{ON} to enable, @code{OFF} to disable. If
21745 enabled, the debug registers values are shown when GDB inserts or
21746 removes a hardware breakpoint or watchpoint, and when the inferior
21747 triggers a hardware-assisted breakpoint or watchpoint.
21749 @kindex maint space
21750 @cindex memory used by commands
21752 Control whether to display memory usage for each command. If set to a
21753 nonzero value, @value{GDBN} will display how much memory each command
21754 took, following the command's own output. This can also be requested
21755 by invoking @value{GDBN} with the @option{--statistics} command-line
21756 switch (@pxref{Mode Options}).
21759 @cindex time of command execution
21761 Control whether to display the execution time for each command. If
21762 set to a nonzero value, @value{GDBN} will display how much time it
21763 took to execute each command, following the command's own output.
21764 This can also be requested by invoking @value{GDBN} with the
21765 @option{--statistics} command-line switch (@pxref{Mode Options}).
21767 @kindex maint translate-address
21768 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
21769 Find the symbol stored at the location specified by the address
21770 @var{addr} and an optional section name @var{section}. If found,
21771 @value{GDBN} prints the name of the closest symbol and an offset from
21772 the symbol's location to the specified address. This is similar to
21773 the @code{info address} command (@pxref{Symbols}), except that this
21774 command also allows to find symbols in other sections.
21778 The following command is useful for non-interactive invocations of
21779 @value{GDBN}, such as in the test suite.
21782 @item set watchdog @var{nsec}
21783 @kindex set watchdog
21784 @cindex watchdog timer
21785 @cindex timeout for commands
21786 Set the maximum number of seconds @value{GDBN} will wait for the
21787 target operation to finish. If this time expires, @value{GDBN}
21788 reports and error and the command is aborted.
21790 @item show watchdog
21791 Show the current setting of the target wait timeout.
21794 @node Remote Protocol
21795 @appendix @value{GDBN} Remote Serial Protocol
21800 * Stop Reply Packets::
21801 * General Query Packets::
21802 * Register Packet Format::
21804 * File-I/O remote protocol extension::
21810 There may be occasions when you need to know something about the
21811 protocol---for example, if there is only one serial port to your target
21812 machine, you might want your program to do something special if it
21813 recognizes a packet meant for @value{GDBN}.
21815 In the examples below, @samp{->} and @samp{<-} are used to indicate
21816 transmitted and received data respectfully.
21818 @cindex protocol, @value{GDBN} remote serial
21819 @cindex serial protocol, @value{GDBN} remote
21820 @cindex remote serial protocol
21821 All @value{GDBN} commands and responses (other than acknowledgments) are
21822 sent as a @var{packet}. A @var{packet} is introduced with the character
21823 @samp{$}, the actual @var{packet-data}, and the terminating character
21824 @samp{#} followed by a two-digit @var{checksum}:
21827 @code{$}@var{packet-data}@code{#}@var{checksum}
21831 @cindex checksum, for @value{GDBN} remote
21833 The two-digit @var{checksum} is computed as the modulo 256 sum of all
21834 characters between the leading @samp{$} and the trailing @samp{#} (an
21835 eight bit unsigned checksum).
21837 Implementors should note that prior to @value{GDBN} 5.0 the protocol
21838 specification also included an optional two-digit @var{sequence-id}:
21841 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
21844 @cindex sequence-id, for @value{GDBN} remote
21846 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
21847 has never output @var{sequence-id}s. Stubs that handle packets added
21848 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
21850 @cindex acknowledgment, for @value{GDBN} remote
21851 When either the host or the target machine receives a packet, the first
21852 response expected is an acknowledgment: either @samp{+} (to indicate
21853 the package was received correctly) or @samp{-} (to request
21857 -> @code{$}@var{packet-data}@code{#}@var{checksum}
21862 The host (@value{GDBN}) sends @var{command}s, and the target (the
21863 debugging stub incorporated in your program) sends a @var{response}. In
21864 the case of step and continue @var{command}s, the response is only sent
21865 when the operation has completed (the target has again stopped).
21867 @var{packet-data} consists of a sequence of characters with the
21868 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
21871 Fields within the packet should be separated using @samp{,} @samp{;} or
21872 @cindex remote protocol, field separator
21873 @samp{:}. Except where otherwise noted all numbers are represented in
21874 @sc{hex} with leading zeros suppressed.
21876 Implementors should note that prior to @value{GDBN} 5.0, the character
21877 @samp{:} could not appear as the third character in a packet (as it
21878 would potentially conflict with the @var{sequence-id}).
21880 Response @var{data} can be run-length encoded to save space. A @samp{*}
21881 means that the next character is an @sc{ascii} encoding giving a repeat count
21882 which stands for that many repetitions of the character preceding the
21883 @samp{*}. The encoding is @code{n+29}, yielding a printable character
21884 where @code{n >=3} (which is where rle starts to win). The printable
21885 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
21886 value greater than 126 should not be used.
21893 means the same as "0000".
21895 The error response returned for some packets includes a two character
21896 error number. That number is not well defined.
21898 For any @var{command} not supported by the stub, an empty response
21899 (@samp{$#00}) should be returned. That way it is possible to extend the
21900 protocol. A newer @value{GDBN} can tell if a packet is supported based
21903 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
21904 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
21910 The following table provides a complete list of all currently defined
21911 @var{command}s and their corresponding response @var{data}.
21912 @xref{File-I/O remote protocol extension}, for details about the File
21913 I/O extension of the remote protocol.
21917 @item @code{!} --- extended mode
21918 @cindex @code{!} packet
21920 Enable extended mode. In extended mode, the remote server is made
21921 persistent. The @samp{R} packet is used to restart the program being
21927 The remote target both supports and has enabled extended mode.
21930 @item @code{?} --- last signal
21931 @cindex @code{?} packet
21933 Indicate the reason the target halted. The reply is the same as for
21937 @xref{Stop Reply Packets}, for the reply specifications.
21939 @item @code{a} --- reserved
21941 Reserved for future use.
21943 @item @code{A}@var{arglen}@code{,}@var{argnum}@code{,}@var{arg}@code{,@dots{}} --- set program arguments @strong{(reserved)}
21944 @cindex @code{A} packet
21946 Initialized @samp{argv[]} array passed into program. @var{arglen}
21947 specifies the number of bytes in the hex encoded byte stream @var{arg}.
21948 See @code{gdbserver} for more details.
21956 @item @code{b}@var{baud} --- set baud @strong{(deprecated)}
21957 @cindex @code{b} packet
21959 Change the serial line speed to @var{baud}.
21961 JTC: @emph{When does the transport layer state change? When it's
21962 received, or after the ACK is transmitted. In either case, there are
21963 problems if the command or the acknowledgment packet is dropped.}
21965 Stan: @emph{If people really wanted to add something like this, and get
21966 it working for the first time, they ought to modify ser-unix.c to send
21967 some kind of out-of-band message to a specially-setup stub and have the
21968 switch happen "in between" packets, so that from remote protocol's point
21969 of view, nothing actually happened.}
21971 @item @code{B}@var{addr},@var{mode} --- set breakpoint @strong{(deprecated)}
21972 @cindex @code{B} packet
21974 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
21975 breakpoint at @var{addr}.
21977 This packet has been replaced by the @samp{Z} and @samp{z} packets
21978 (@pxref{insert breakpoint or watchpoint packet}).
21980 @item @code{c}@var{addr} --- continue
21981 @cindex @code{c} packet
21983 @var{addr} is address to resume. If @var{addr} is omitted, resume at
21987 @xref{Stop Reply Packets}, for the reply specifications.
21989 @item @code{C}@var{sig}@code{;}@var{addr} --- continue with signal
21990 @cindex @code{C} packet
21992 Continue with signal @var{sig} (hex signal number). If
21993 @code{;}@var{addr} is omitted, resume at same address.
21996 @xref{Stop Reply Packets}, for the reply specifications.
21998 @item @code{d} --- toggle debug @strong{(deprecated)}
21999 @cindex @code{d} packet
22003 @item @code{D} --- detach
22004 @cindex @code{D} packet
22006 Detach @value{GDBN} from the remote system. Sent to the remote target
22007 before @value{GDBN} disconnects via the @code{detach} command.
22011 @item @emph{no response}
22012 @value{GDBN} does not check for any response after sending this packet.
22015 @item @code{e} --- reserved
22017 Reserved for future use.
22019 @item @code{E} --- reserved
22021 Reserved for future use.
22023 @item @code{f} --- reserved
22025 Reserved for future use.
22027 @item @code{F}@var{RC}@code{,}@var{EE}@code{,}@var{CF}@code{;}@var{XX} --- Reply to target's F packet.
22028 @cindex @code{F} packet
22030 This packet is send by @value{GDBN} as reply to a @code{F} request packet
22031 sent by the target. This is part of the File-I/O protocol extension.
22032 @xref{File-I/O remote protocol extension}, for the specification.
22034 @item @code{g} --- read registers
22035 @anchor{read registers packet}
22036 @cindex @code{g} packet
22038 Read general registers.
22042 @item @var{XX@dots{}}
22043 Each byte of register data is described by two hex digits. The bytes
22044 with the register are transmitted in target byte order. The size of
22045 each register and their position within the @samp{g} @var{packet} are
22046 determined by the @value{GDBN} internal macros
22047 @var{DEPRECATED_REGISTER_RAW_SIZE} and @var{REGISTER_NAME} macros. The
22048 specification of several standard @code{g} packets is specified below.
22053 @item @code{G}@var{XX@dots{}} --- write regs
22054 @cindex @code{G} packet
22056 @xref{read registers packet}, for a description of the @var{XX@dots{}}
22067 @item @code{h} --- reserved
22069 Reserved for future use.
22071 @item @code{H}@var{c}@var{t@dots{}} --- set thread
22072 @cindex @code{H} packet
22074 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
22075 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
22076 should be @samp{c} for step and continue operations, @samp{g} for other
22077 operations. The thread designator @var{t@dots{}} may be -1, meaning all
22078 the threads, a thread number, or zero which means pick any thread.
22089 @c 'H': How restrictive (or permissive) is the thread model. If a
22090 @c thread is selected and stopped, are other threads allowed
22091 @c to continue to execute? As I mentioned above, I think the
22092 @c semantics of each command when a thread is selected must be
22093 @c described. For example:
22095 @c 'g': If the stub supports threads and a specific thread is
22096 @c selected, returns the register block from that thread;
22097 @c otherwise returns current registers.
22099 @c 'G' If the stub supports threads and a specific thread is
22100 @c selected, sets the registers of the register block of
22101 @c that thread; otherwise sets current registers.
22103 @item @code{i}@var{addr}@code{,}@var{nnn} --- cycle step @strong{(draft)}
22104 @anchor{cycle step packet}
22105 @cindex @code{i} packet
22107 Step the remote target by a single clock cycle. If @code{,}@var{nnn} is
22108 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
22109 step starting at that address.
22111 @item @code{I} --- signal then cycle step @strong{(reserved)}
22112 @cindex @code{I} packet
22114 @xref{step with signal packet}. @xref{cycle step packet}.
22116 @item @code{j} --- reserved
22118 Reserved for future use.
22120 @item @code{J} --- reserved
22122 Reserved for future use.
22124 @item @code{k} --- kill request
22125 @cindex @code{k} packet
22127 FIXME: @emph{There is no description of how to operate when a specific
22128 thread context has been selected (i.e.@: does 'k' kill only that
22131 @item @code{K} --- reserved
22133 Reserved for future use.
22135 @item @code{l} --- reserved
22137 Reserved for future use.
22139 @item @code{L} --- reserved
22141 Reserved for future use.
22143 @item @code{m}@var{addr}@code{,}@var{length} --- read memory
22144 @cindex @code{m} packet
22146 Read @var{length} bytes of memory starting at address @var{addr}.
22147 Neither @value{GDBN} nor the stub assume that sized memory transfers are
22148 assumed using word aligned accesses. FIXME: @emph{A word aligned memory
22149 transfer mechanism is needed.}
22153 @item @var{XX@dots{}}
22154 @var{XX@dots{}} is mem contents. Can be fewer bytes than requested if able
22155 to read only part of the data. Neither @value{GDBN} nor the stub assume
22156 that sized memory transfers are assumed using word aligned
22157 accesses. FIXME: @emph{A word aligned memory transfer mechanism is
22163 @item @code{M}@var{addr},@var{length}@code{:}@var{XX@dots{}} --- write mem
22164 @cindex @code{M} packet
22166 Write @var{length} bytes of memory starting at address @var{addr}.
22167 @var{XX@dots{}} is the data.
22174 for an error (this includes the case where only part of the data was
22178 @item @code{n} --- reserved
22180 Reserved for future use.
22182 @item @code{N} --- reserved
22184 Reserved for future use.
22186 @item @code{o} --- reserved
22188 Reserved for future use.
22190 @item @code{O} --- reserved
22192 @item @code{p}@var{hex number of register} --- read register packet
22193 @cindex @code{p} packet
22195 @xref{read registers packet}, for a description of how the returned
22196 register value is encoded.
22200 @item @var{XX@dots{}}
22201 the register's value
22205 Indicating an unrecognized @var{query}.
22208 @item @code{P}@var{n@dots{}}@code{=}@var{r@dots{}} --- write register
22209 @anchor{write register packet}
22210 @cindex @code{P} packet
22212 Write register @var{n@dots{}} with value @var{r@dots{}}, which contains two hex
22213 digits for each byte in the register (target byte order).
22223 @item @code{q}@var{query} --- general query
22224 @anchor{general query packet}
22225 @cindex @code{q} packet
22227 Request info about @var{query}. In general @value{GDBN} queries have a
22228 leading upper case letter. Custom vendor queries should use a company
22229 prefix (in lower case) ex: @samp{qfsf.var}. @var{query} may optionally
22230 be followed by a @samp{,} or @samp{;} separated list. Stubs must ensure
22231 that they match the full @var{query} name.
22235 @item @var{XX@dots{}}
22236 Hex encoded data from query. The reply can not be empty.
22240 Indicating an unrecognized @var{query}.
22243 @item @code{Q}@var{var}@code{=}@var{val} --- general set
22244 @cindex @code{Q} packet
22246 Set value of @var{var} to @var{val}.
22248 @xref{general query packet}, for a discussion of naming conventions.
22250 @item @code{r} --- reset @strong{(deprecated)}
22251 @cindex @code{r} packet
22253 Reset the entire system.
22255 @item @code{R}@var{XX} --- remote restart
22256 @cindex @code{R} packet
22258 Restart the program being debugged. @var{XX}, while needed, is ignored.
22259 This packet is only available in extended mode.
22263 @item @emph{no reply}
22264 The @samp{R} packet has no reply.
22267 @item @code{s}@var{addr} --- step
22268 @cindex @code{s} packet
22270 @var{addr} is address to resume. If @var{addr} is omitted, resume at
22274 @xref{Stop Reply Packets}, for the reply specifications.
22276 @item @code{S}@var{sig}@code{;}@var{addr} --- step with signal
22277 @anchor{step with signal packet}
22278 @cindex @code{S} packet
22280 Like @samp{C} but step not continue.
22283 @xref{Stop Reply Packets}, for the reply specifications.
22285 @item @code{t}@var{addr}@code{:}@var{PP}@code{,}@var{MM} --- search
22286 @cindex @code{t} packet
22288 Search backwards starting at address @var{addr} for a match with pattern
22289 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
22290 @var{addr} must be at least 3 digits.
22292 @item @code{T}@var{XX} --- thread alive
22293 @cindex @code{T} packet
22295 Find out if the thread XX is alive.
22300 thread is still alive
22305 @item @code{u} --- reserved
22307 Reserved for future use.
22309 @item @code{U} --- reserved
22311 Reserved for future use.
22313 @item @code{v} --- verbose packet prefix
22315 Packets starting with @code{v} are identified by a multi-letter name,
22316 up to the first @code{;} or @code{?} (or the end of the packet).
22318 @item @code{vCont}[;@var{action}[@code{:}@var{tid}]]... --- extended resume
22319 @cindex @code{vCont} packet
22321 Resume the inferior. Different actions may be specified for each thread.
22322 If an action is specified with no @var{tid}, then it is applied to any
22323 threads that don't have a specific action specified; if no default action is
22324 specified then other threads should remain stopped. Specifying multiple
22325 default actions is an error; specifying no actions is also an error.
22326 Thread IDs are specified in hexadecimal. Currently supported actions are:
22332 Continue with signal @var{sig}. @var{sig} should be two hex digits.
22336 Step with signal @var{sig}. @var{sig} should be two hex digits.
22339 The optional @var{addr} argument normally associated with these packets is
22340 not supported in @code{vCont}.
22343 @xref{Stop Reply Packets}, for the reply specifications.
22345 @item @code{vCont?} --- extended resume query
22346 @cindex @code{vCont?} packet
22348 Query support for the @code{vCont} packet.
22352 @item @code{vCont}[;@var{action}]...
22353 The @code{vCont} packet is supported. Each @var{action} is a supported
22354 command in the @code{vCont} packet.
22356 The @code{vCont} packet is not supported.
22359 @item @code{V} --- reserved
22361 Reserved for future use.
22363 @item @code{w} --- reserved
22365 Reserved for future use.
22367 @item @code{W} --- reserved
22369 Reserved for future use.
22371 @item @code{x} --- reserved
22373 Reserved for future use.
22375 @item @code{X}@var{addr}@code{,}@var{length}@var{:}@var{XX@dots{}} --- write mem (binary)
22376 @cindex @code{X} packet
22378 @var{addr} is address, @var{length} is number of bytes, @var{XX@dots{}}
22379 is binary data. The characters @code{$}, @code{#}, and @code{0x7d} are
22380 escaped using @code{0x7d}, and then XORed with @code{0x20}.
22381 For example, @code{0x7d} would be transmitted as @code{0x7d 0x5d}.
22391 @item @code{y} --- reserved
22393 Reserved for future use.
22395 @item @code{Y} reserved
22397 Reserved for future use.
22399 @item @code{z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- remove breakpoint or watchpoint @strong{(draft)}
22400 @itemx @code{Z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- insert breakpoint or watchpoint @strong{(draft)}
22401 @anchor{insert breakpoint or watchpoint packet}
22402 @cindex @code{z} packet
22403 @cindex @code{Z} packets
22405 Insert (@code{Z}) or remove (@code{z}) a @var{type} breakpoint or
22406 watchpoint starting at address @var{address} and covering the next
22407 @var{length} bytes.
22409 Each breakpoint and watchpoint packet @var{type} is documented
22412 @emph{Implementation notes: A remote target shall return an empty string
22413 for an unrecognized breakpoint or watchpoint packet @var{type}. A
22414 remote target shall support either both or neither of a given
22415 @code{Z}@var{type}@dots{} and @code{z}@var{type}@dots{} packet pair. To
22416 avoid potential problems with duplicate packets, the operations should
22417 be implemented in an idempotent way.}
22419 @item @code{z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- remove memory breakpoint @strong{(draft)}
22420 @item @code{Z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- insert memory breakpoint @strong{(draft)}
22421 @cindex @code{z0} packet
22422 @cindex @code{Z0} packet
22424 Insert (@code{Z0}) or remove (@code{z0}) a memory breakpoint at address
22425 @code{addr} of size @code{length}.
22427 A memory breakpoint is implemented by replacing the instruction at
22428 @var{addr} with a software breakpoint or trap instruction. The
22429 @code{length} is used by targets that indicates the size of the
22430 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
22431 @sc{mips} can insert either a 2 or 4 byte breakpoint).
22433 @emph{Implementation note: It is possible for a target to copy or move
22434 code that contains memory breakpoints (e.g., when implementing
22435 overlays). The behavior of this packet, in the presence of such a
22436 target, is not defined.}
22448 @item @code{z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- remove hardware breakpoint @strong{(draft)}
22449 @item @code{Z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- insert hardware breakpoint @strong{(draft)}
22450 @cindex @code{z1} packet
22451 @cindex @code{Z1} packet
22453 Insert (@code{Z1}) or remove (@code{z1}) a hardware breakpoint at
22454 address @code{addr} of size @code{length}.
22456 A hardware breakpoint is implemented using a mechanism that is not
22457 dependant on being able to modify the target's memory.
22459 @emph{Implementation note: A hardware breakpoint is not affected by code
22472 @item @code{z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- remove write watchpoint @strong{(draft)}
22473 @item @code{Z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- insert write watchpoint @strong{(draft)}
22474 @cindex @code{z2} packet
22475 @cindex @code{Z2} packet
22477 Insert (@code{Z2}) or remove (@code{z2}) a write watchpoint.
22489 @item @code{z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- remove read watchpoint @strong{(draft)}
22490 @item @code{Z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- insert read watchpoint @strong{(draft)}
22491 @cindex @code{z3} packet
22492 @cindex @code{Z3} packet
22494 Insert (@code{Z3}) or remove (@code{z3}) a read watchpoint.
22506 @item @code{z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- remove access watchpoint @strong{(draft)}
22507 @item @code{Z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- insert access watchpoint @strong{(draft)}
22508 @cindex @code{z4} packet
22509 @cindex @code{Z4} packet
22511 Insert (@code{Z4}) or remove (@code{z4}) an access watchpoint.
22525 @node Stop Reply Packets
22526 @section Stop Reply Packets
22527 @cindex stop reply packets
22529 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
22530 receive any of the below as a reply. In the case of the @samp{C},
22531 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
22532 when the target halts. In the below the exact meaning of @samp{signal
22533 number} is poorly defined. In general one of the UNIX signal numbering
22534 conventions is used.
22539 @var{AA} is the signal number
22541 @item @code{T}@var{AA}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}
22542 @cindex @code{T} packet reply
22544 @var{AA} = two hex digit signal number; @var{n...} = register number
22545 (hex), @var{r...} = target byte ordered register contents, size defined
22546 by @code{DEPRECATED_REGISTER_RAW_SIZE}; @var{n...} = @samp{thread},
22547 @var{r...} = thread process ID, this is a hex integer; @var{n...} =
22548 (@samp{watch} | @samp{rwatch} | @samp{awatch}, @var{r...} = data
22549 address, this is a hex integer; @var{n...} = other string not starting
22550 with valid hex digit. @value{GDBN} should ignore this @var{n...},
22551 @var{r...} pair and go on to the next. This way we can extend the
22556 The process exited, and @var{AA} is the exit status. This is only
22557 applicable to certain targets.
22561 The process terminated with signal @var{AA}.
22563 @item O@var{XX@dots{}}
22565 @var{XX@dots{}} is hex encoding of @sc{ascii} data. This can happen at
22566 any time while the program is running and the debugger should continue
22567 to wait for @samp{W}, @samp{T}, etc.
22569 @item F@var{call-id}@code{,}@var{parameter@dots{}}
22571 @var{call-id} is the identifier which says which host system call should
22572 be called. This is just the name of the function. Translation into the
22573 correct system call is only applicable as it's defined in @value{GDBN}.
22574 @xref{File-I/O remote protocol extension}, for a list of implemented
22577 @var{parameter@dots{}} is a list of parameters as defined for this very
22580 The target replies with this packet when it expects @value{GDBN} to call
22581 a host system call on behalf of the target. @value{GDBN} replies with
22582 an appropriate @code{F} packet and keeps up waiting for the next reply
22583 packet from the target. The latest @samp{C}, @samp{c}, @samp{S} or
22584 @samp{s} action is expected to be continued.
22585 @xref{File-I/O remote protocol extension}, for more details.
22589 @node General Query Packets
22590 @section General Query Packets
22591 @cindex remote query requests
22593 The following set and query packets have already been defined.
22597 @item @code{q}@code{C} --- current thread
22598 @cindex current thread, remote request
22599 @cindex @code{qC} packet
22600 Return the current thread id.
22604 @item @code{QC}@var{pid}
22605 Where @var{pid} is an unsigned hexidecimal process id.
22607 Any other reply implies the old pid.
22610 @item @code{q}@code{fThreadInfo} -- all thread ids
22611 @cindex list active threads, remote request
22612 @cindex @code{qfThreadInfo} packet
22613 @code{q}@code{sThreadInfo}
22615 Obtain a list of active thread ids from the target (OS). Since there
22616 may be too many active threads to fit into one reply packet, this query
22617 works iteratively: it may require more than one query/reply sequence to
22618 obtain the entire list of threads. The first query of the sequence will
22619 be the @code{qf}@code{ThreadInfo} query; subsequent queries in the
22620 sequence will be the @code{qs}@code{ThreadInfo} query.
22622 NOTE: replaces the @code{qL} query (see below).
22626 @item @code{m}@var{id}
22628 @item @code{m}@var{id},@var{id}@dots{}
22629 a comma-separated list of thread ids
22631 (lower case 'el') denotes end of list.
22634 In response to each query, the target will reply with a list of one or
22635 more thread ids, in big-endian unsigned hex, separated by commas.
22636 @value{GDBN} will respond to each reply with a request for more thread
22637 ids (using the @code{qs} form of the query), until the target responds
22638 with @code{l} (lower-case el, for @code{'last'}).
22640 @item @code{q}@code{ThreadExtraInfo}@code{,}@var{id} --- extra thread info
22641 @cindex thread attributes info, remote request
22642 @cindex @code{qThreadExtraInfo} packet
22643 Where @var{id} is a thread-id in big-endian hex. Obtain a printable
22644 string description of a thread's attributes from the target OS. This
22645 string may contain anything that the target OS thinks is interesting for
22646 @value{GDBN} to tell the user about the thread. The string is displayed
22647 in @value{GDBN}'s @samp{info threads} display. Some examples of
22648 possible thread extra info strings are ``Runnable'', or ``Blocked on
22653 @item @var{XX@dots{}}
22654 Where @var{XX@dots{}} is a hex encoding of @sc{ascii} data, comprising
22655 the printable string containing the extra information about the thread's
22659 @item @code{q}@code{L}@var{startflag}@var{threadcount}@var{nextthread} --- query @var{LIST} or @var{threadLIST} @strong{(deprecated)}
22661 Obtain thread information from RTOS. Where: @var{startflag} (one hex
22662 digit) is one to indicate the first query and zero to indicate a
22663 subsequent query; @var{threadcount} (two hex digits) is the maximum
22664 number of threads the response packet can contain; and @var{nextthread}
22665 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
22666 returned in the response as @var{argthread}.
22668 NOTE: this query is replaced by the @code{q}@code{fThreadInfo} query
22673 @item @code{q}@code{M}@var{count}@var{done}@var{argthread}@var{thread@dots{}}
22674 Where: @var{count} (two hex digits) is the number of threads being
22675 returned; @var{done} (one hex digit) is zero to indicate more threads
22676 and one indicates no further threads; @var{argthreadid} (eight hex
22677 digits) is @var{nextthread} from the request packet; @var{thread@dots{}}
22678 is a sequence of thread IDs from the target. @var{threadid} (eight hex
22679 digits). See @code{remote.c:parse_threadlist_response()}.
22682 @item @code{q}@code{CRC:}@var{addr}@code{,}@var{length} --- compute CRC of memory block
22683 @cindex CRC of memory block, remote request
22684 @cindex @code{qCRC} packet
22687 @item @code{E}@var{NN}
22688 An error (such as memory fault)
22689 @item @code{C}@var{CRC32}
22690 A 32 bit cyclic redundancy check of the specified memory region.
22693 @item @code{q}@code{Offsets} --- query sect offs
22694 @cindex section offsets, remote request
22695 @cindex @code{qOffsets} packet
22696 Get section offsets that the target used when re-locating the downloaded
22697 image. @emph{Note: while a @code{Bss} offset is included in the
22698 response, @value{GDBN} ignores this and instead applies the @code{Data}
22699 offset to the @code{Bss} section.}
22703 @item @code{Text=}@var{xxx}@code{;Data=}@var{yyy}@code{;Bss=}@var{zzz}
22706 @item @code{q}@code{P}@var{mode}@var{threadid} --- thread info request
22707 @cindex thread information, remote request
22708 @cindex @code{qP} packet
22709 Returns information on @var{threadid}. Where: @var{mode} is a hex
22710 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
22717 See @code{remote.c:remote_unpack_thread_info_response()}.
22719 @item @code{q}@code{Rcmd,}@var{command} --- remote command
22720 @cindex execute remote command, remote request
22721 @cindex @code{qRcmd} packet
22722 @var{command} (hex encoded) is passed to the local interpreter for
22723 execution. Invalid commands should be reported using the output string.
22724 Before the final result packet, the target may also respond with a
22725 number of intermediate @code{O}@var{output} console output packets.
22726 @emph{Implementors should note that providing access to a stubs's
22727 interpreter may have security implications}.
22732 A command response with no output.
22734 A command response with the hex encoded output string @var{OUTPUT}.
22735 @item @code{E}@var{NN}
22736 Indicate a badly formed request.
22738 When @samp{q}@samp{Rcmd} is not recognized.
22741 @item @code{qSymbol::} --- symbol lookup
22742 @cindex symbol lookup, remote request
22743 @cindex @code{qSymbol} packet
22744 Notify the target that @value{GDBN} is prepared to serve symbol lookup
22745 requests. Accept requests from the target for the values of symbols.
22750 The target does not need to look up any (more) symbols.
22751 @item @code{qSymbol:}@var{sym_name}
22752 The target requests the value of symbol @var{sym_name} (hex encoded).
22753 @value{GDBN} may provide the value by using the
22754 @code{qSymbol:}@var{sym_value}:@var{sym_name} message, described below.
22757 @item @code{qSymbol:}@var{sym_value}:@var{sym_name} --- symbol value
22759 Set the value of @var{sym_name} to @var{sym_value}.
22761 @var{sym_name} (hex encoded) is the name of a symbol whose value the
22762 target has previously requested.
22764 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
22765 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
22771 The target does not need to look up any (more) symbols.
22772 @item @code{qSymbol:}@var{sym_name}
22773 The target requests the value of a new symbol @var{sym_name} (hex
22774 encoded). @value{GDBN} will continue to supply the values of symbols
22775 (if available), until the target ceases to request them.
22778 @item @code{qPart}:@var{object}:@code{read}:@var{annex}:@var{offset},@var{length} --- read special data
22779 @cindex read special object, remote request
22780 @cindex @code{qPart} packet
22781 Read uninterpreted bytes from the target's special data area
22782 identified by the keyword @code{object}.
22783 Request @var{length} bytes starting at @var{offset} bytes into the data.
22784 The content and encoding of @var{annex} is specific to the object;
22785 it can supply additional details about what data to access.
22787 Here are the specific requests of this form defined so far.
22788 All @samp{@code{qPart}:@var{object}:@code{read}:@dots{}}
22789 requests use the same reply formats, listed below.
22792 @item @code{qPart}:@code{auxv}:@code{read}::@var{offset},@var{length}
22793 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
22794 auxiliary vector}, and see @ref{Remote configuration,
22795 read-aux-vector-packet}. Note @var{annex} must be empty.
22801 The @var{offset} in the request is at the end of the data.
22802 There is no more data to be read.
22804 @item @var{XX@dots{}}
22805 Hex encoded data bytes read.
22806 This may be fewer bytes than the @var{length} in the request.
22809 The request was malformed, or @var{annex} was invalid.
22811 @item @code{E}@var{nn}
22812 The offset was invalid, or there was an error encountered reading the data.
22813 @var{nn} is a hex-encoded @code{errno} value.
22815 @item @code{""} (empty)
22816 An empty reply indicates the @var{object} or @var{annex} string was not
22817 recognized by the stub.
22820 @item @code{qPart}:@var{object}:@code{write}:@var{annex}:@var{offset}:@var{data@dots{}}
22821 @cindex write data into object, remote request
22822 Write uninterpreted bytes into the target's special data area
22823 identified by the keyword @code{object},
22824 starting at @var{offset} bytes into the data.
22825 @var{data@dots{}} is the hex-encoded data to be written.
22826 The content and encoding of @var{annex} is specific to the object;
22827 it can supply additional details about what data to access.
22829 No requests of this form are presently in use. This specification
22830 serves as a placeholder to document the common format that new
22831 specific request specifications ought to use.
22836 @var{nn} (hex encoded) is the number of bytes written.
22837 This may be fewer bytes than supplied in the request.
22840 The request was malformed, or @var{annex} was invalid.
22842 @item @code{E}@var{nn}
22843 The offset was invalid, or there was an error encountered writing the data.
22844 @var{nn} is a hex-encoded @code{errno} value.
22846 @item @code{""} (empty)
22847 An empty reply indicates the @var{object} or @var{annex} string was not
22848 recognized by the stub, or that the object does not support writing.
22851 @item @code{qPart}:@var{object}:@var{operation}:@dots{}
22852 Requests of this form may be added in the future. When a stub does
22853 not recognize the @var{object} keyword, or its support for
22854 @var{object} does not recognize the @var{operation} keyword,
22855 the stub must respond with an empty packet.
22857 @item @code{qGetTLSAddr}:@var{thread-id},@var{offset},@var{lm} --- get thread local storage address
22858 @cindex get thread-local storage address, remote request
22859 @cindex @code{qGetTLSAddr} packet
22860 Fetch the address associated with thread local storage specified
22861 by @var{thread-id}, @var{offset}, and @var{lm}.
22863 @var{thread-id} is the (big endian, hex encoded) thread id associated with the
22864 thread for which to fetch the TLS address.
22866 @var{offset} is the (big endian, hex encoded) offset associated with the
22867 thread local variable. (This offset is obtained from the debug
22868 information associated with the variable.)
22870 @var{lm} is the (big endian, hex encoded) OS/ABI specific encoding of the
22871 the load module associated with the thread local storage. For example,
22872 a @sc{gnu}/Linux system will pass the link map address of the shared
22873 object associated with the thread local storage under consideration.
22874 Other operating environments may choose to represent the load module
22875 differently, so the precise meaning of this parameter will vary.
22879 @item @var{XX@dots{}}
22880 Hex encoded (big endian) bytes representing the address of the thread
22881 local storage requested.
22883 @item @code{E}@var{nn} (where @var{nn} are hex digits)
22886 @item @code{""} (empty)
22887 An empty reply indicates that @code{qGetTLSAddr} is not supported by the stub.
22890 Use of this request packet is controlled by the @code{set remote
22891 get-thread-local-storage-address} command (@pxref{Remote
22892 configuration, set remote get-thread-local-storage-address}).
22896 @node Register Packet Format
22897 @section Register Packet Format
22899 The following @samp{g}/@samp{G} packets have previously been defined.
22900 In the below, some thirty-two bit registers are transferred as
22901 sixty-four bits. Those registers should be zero/sign extended (which?)
22902 to fill the space allocated. Register bytes are transfered in target
22903 byte order. The two nibbles within a register byte are transfered
22904 most-significant - least-significant.
22910 All registers are transfered as thirty-two bit quantities in the order:
22911 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
22912 registers; fsr; fir; fp.
22916 All registers are transfered as sixty-four bit quantities (including
22917 thirty-two bit registers such as @code{sr}). The ordering is the same
22925 Example sequence of a target being re-started. Notice how the restart
22926 does not get any direct output:
22931 @emph{target restarts}
22934 <- @code{T001:1234123412341234}
22938 Example sequence of a target being stepped by a single instruction:
22941 -> @code{G1445@dots{}}
22946 <- @code{T001:1234123412341234}
22950 <- @code{1455@dots{}}
22954 @node File-I/O remote protocol extension
22955 @section File-I/O remote protocol extension
22956 @cindex File-I/O remote protocol extension
22959 * File-I/O Overview::
22960 * Protocol basics::
22961 * The F request packet::
22962 * The F reply packet::
22963 * Memory transfer::
22964 * The Ctrl-C message::
22966 * The isatty call::
22967 * The system call::
22968 * List of supported calls::
22969 * Protocol specific representation of datatypes::
22971 * File-I/O Examples::
22974 @node File-I/O Overview
22975 @subsection File-I/O Overview
22976 @cindex file-i/o overview
22978 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
22979 target to use the host's file system and console I/O when calling various
22980 system calls. System calls on the target system are translated into a
22981 remote protocol packet to the host system which then performs the needed
22982 actions and returns with an adequate response packet to the target system.
22983 This simulates file system operations even on targets that lack file systems.
22985 The protocol is defined host- and target-system independent. It uses
22986 its own independent representation of datatypes and values. Both,
22987 @value{GDBN} and the target's @value{GDBN} stub are responsible for
22988 translating the system dependent values into the unified protocol values
22989 when data is transmitted.
22991 The communication is synchronous. A system call is possible only
22992 when GDB is waiting for the @samp{C}, @samp{c}, @samp{S} or @samp{s}
22993 packets. While @value{GDBN} handles the request for a system call,
22994 the target is stopped to allow deterministic access to the target's
22995 memory. Therefore File-I/O is not interuptible by target signals. It
22996 is possible to interrupt File-I/O by a user interrupt (Ctrl-C), though.
22998 The target's request to perform a host system call does not finish
22999 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
23000 after finishing the system call, the target returns to continuing the
23001 previous activity (continue, step). No additional continue or step
23002 request from @value{GDBN} is required.
23005 (@value{GDBP}) continue
23006 <- target requests 'system call X'
23007 target is stopped, @value{GDBN} executes system call
23008 -> GDB returns result
23009 ... target continues, GDB returns to wait for the target
23010 <- target hits breakpoint and sends a Txx packet
23013 The protocol is only used for files on the host file system and
23014 for I/O on the console. Character or block special devices, pipes,
23015 named pipes or sockets or any other communication method on the host
23016 system are not supported by this protocol.
23018 @node Protocol basics
23019 @subsection Protocol basics
23020 @cindex protocol basics, file-i/o
23022 The File-I/O protocol uses the @code{F} packet, as request as well
23023 as as reply packet. Since a File-I/O system call can only occur when
23024 @value{GDBN} is waiting for the continuing or stepping target, the
23025 File-I/O request is a reply that @value{GDBN} has to expect as a result
23026 of a former @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
23027 This @code{F} packet contains all information needed to allow @value{GDBN}
23028 to call the appropriate host system call:
23032 A unique identifier for the requested system call.
23035 All parameters to the system call. Pointers are given as addresses
23036 in the target memory address space. Pointers to strings are given as
23037 pointer/length pair. Numerical values are given as they are.
23038 Numerical control values are given in a protocol specific representation.
23042 At that point @value{GDBN} has to perform the following actions.
23046 If parameter pointer values are given, which point to data needed as input
23047 to a system call, @value{GDBN} requests this data from the target with a
23048 standard @code{m} packet request. This additional communication has to be
23049 expected by the target implementation and is handled as any other @code{m}
23053 @value{GDBN} translates all value from protocol representation to host
23054 representation as needed. Datatypes are coerced into the host types.
23057 @value{GDBN} calls the system call
23060 It then coerces datatypes back to protocol representation.
23063 If pointer parameters in the request packet point to buffer space in which
23064 a system call is expected to copy data to, the data is transmitted to the
23065 target using a @code{M} or @code{X} packet. This packet has to be expected
23066 by the target implementation and is handled as any other @code{M} or @code{X}
23071 Eventually @value{GDBN} replies with another @code{F} packet which contains all
23072 necessary information for the target to continue. This at least contains
23079 @code{errno}, if has been changed by the system call.
23086 After having done the needed type and value coercion, the target continues
23087 the latest continue or step action.
23089 @node The F request packet
23090 @subsection The @code{F} request packet
23091 @cindex file-i/o request packet
23092 @cindex @code{F} request packet
23094 The @code{F} request packet has the following format:
23099 @code{F}@var{call-id}@code{,}@var{parameter@dots{}}
23102 @var{call-id} is the identifier to indicate the host system call to be called.
23103 This is just the name of the function.
23105 @var{parameter@dots{}} are the parameters to the system call.
23109 Parameters are hexadecimal integer values, either the real values in case
23110 of scalar datatypes, as pointers to target buffer space in case of compound
23111 datatypes and unspecified memory areas or as pointer/length pairs in case
23112 of string parameters. These are appended to the call-id, each separated
23113 from its predecessor by a comma. All values are transmitted in ASCII
23114 string representation, pointer/length pairs separated by a slash.
23116 @node The F reply packet
23117 @subsection The @code{F} reply packet
23118 @cindex file-i/o reply packet
23119 @cindex @code{F} reply packet
23121 The @code{F} reply packet has the following format:
23126 @code{F}@var{retcode}@code{,}@var{errno}@code{,}@var{Ctrl-C flag}@code{;}@var{call specific attachment}
23129 @var{retcode} is the return code of the system call as hexadecimal value.
23131 @var{errno} is the errno set by the call, in protocol specific representation.
23132 This parameter can be omitted if the call was successful.
23134 @var{Ctrl-C flag} is only send if the user requested a break. In this
23135 case, @var{errno} must be send as well, even if the call was successful.
23136 The @var{Ctrl-C flag} itself consists of the character 'C':
23143 or, if the call was interupted before the host call has been performed:
23150 assuming 4 is the protocol specific representation of @code{EINTR}.
23154 @node Memory transfer
23155 @subsection Memory transfer
23156 @cindex memory transfer, in file-i/o protocol
23158 Structured data which is transferred using a memory read or write as e.g.@:
23159 a @code{struct stat} is expected to be in a protocol specific format with
23160 all scalar multibyte datatypes being big endian. This should be done by
23161 the target before the @code{F} packet is sent resp.@: by @value{GDBN} before
23162 it transfers memory to the target. Transferred pointers to structured
23163 data should point to the already coerced data at any time.
23165 @node The Ctrl-C message
23166 @subsection The Ctrl-C message
23167 @cindex ctrl-c message, in file-i/o protocol
23169 A special case is, if the @var{Ctrl-C flag} is set in the @value{GDBN}
23170 reply packet. In this case the target should behave, as if it had
23171 gotten a break message. The meaning for the target is ``system call
23172 interupted by @code{SIGINT}''. Consequentially, the target should actually stop
23173 (as with a break message) and return to @value{GDBN} with a @code{T02}
23174 packet. In this case, it's important for the target to know, in which
23175 state the system call was interrupted. Since this action is by design
23176 not an atomic operation, we have to differ between two cases:
23180 The system call hasn't been performed on the host yet.
23183 The system call on the host has been finished.
23187 These two states can be distinguished by the target by the value of the
23188 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
23189 call hasn't been performed. This is equivalent to the @code{EINTR} handling
23190 on POSIX systems. In any other case, the target may presume that the
23191 system call has been finished --- successful or not --- and should behave
23192 as if the break message arrived right after the system call.
23194 @value{GDBN} must behave reliable. If the system call has not been called
23195 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
23196 @code{errno} in the packet. If the system call on the host has been finished
23197 before the user requests a break, the full action must be finshed by
23198 @value{GDBN}. This requires sending @code{M} or @code{X} packets as they fit.
23199 The @code{F} packet may only be send when either nothing has happened
23200 or the full action has been completed.
23203 @subsection Console I/O
23204 @cindex console i/o as part of file-i/o
23206 By default and if not explicitely closed by the target system, the file
23207 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
23208 on the @value{GDBN} console is handled as any other file output operation
23209 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
23210 by @value{GDBN} so that after the target read request from file descriptor
23211 0 all following typing is buffered until either one of the following
23216 The user presses @kbd{Ctrl-C}. The behaviour is as explained above, the
23218 system call is treated as finished.
23221 The user presses @kbd{Enter}. This is treated as end of input with a trailing
23225 The user presses @kbd{Ctrl-D}. This is treated as end of input. No trailing
23226 character, especially no Ctrl-D is appended to the input.
23230 If the user has typed more characters as fit in the buffer given to
23231 the read call, the trailing characters are buffered in @value{GDBN} until
23232 either another @code{read(0, @dots{})} is requested by the target or debugging
23233 is stopped on users request.
23235 @node The isatty call
23236 @subsection The @samp{isatty} function call
23237 @cindex isatty call, file-i/o protocol
23239 A special case in this protocol is the library call @code{isatty} which
23240 is implemented as its own call inside of this protocol. It returns
23241 1 to the target if the file descriptor given as parameter is attached
23242 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
23243 would require implementing @code{ioctl} and would be more complex than
23246 @node The system call
23247 @subsection The @samp{system} function call
23248 @cindex system call, file-i/o protocol
23250 The other special case in this protocol is the @code{system} call which
23251 is implemented as its own call, too. @value{GDBN} is taking over the full
23252 task of calling the necessary host calls to perform the @code{system}
23253 call. The return value of @code{system} is simplified before it's returned
23254 to the target. Basically, the only signal transmitted back is @code{EINTR}
23255 in case the user pressed @kbd{Ctrl-C}. Otherwise the return value consists
23256 entirely of the exit status of the called command.
23258 Due to security concerns, the @code{system} call is by default refused
23259 by @value{GDBN}. The user has to allow this call explicitly with the
23260 @kbd{set remote system-call-allowed 1} command.
23263 @item set remote system-call-allowed
23264 @kindex set remote system-call-allowed
23265 Control whether to allow the @code{system} calls in the File I/O
23266 protocol for the remote target. The default is zero (disabled).
23268 @item show remote system-call-allowed
23269 @kindex show remote system-call-allowed
23270 Show the current setting of system calls for the remote File I/O
23274 @node List of supported calls
23275 @subsection List of supported calls
23276 @cindex list of supported file-i/o calls
23293 @unnumberedsubsubsec open
23294 @cindex open, file-i/o system call
23298 int open(const char *pathname, int flags);
23299 int open(const char *pathname, int flags, mode_t mode);
23302 Fopen,pathptr/len,flags,mode
23306 @code{flags} is the bitwise or of the following values:
23310 If the file does not exist it will be created. The host
23311 rules apply as far as file ownership and time stamps
23315 When used with O_CREAT, if the file already exists it is
23316 an error and open() fails.
23319 If the file already exists and the open mode allows
23320 writing (O_RDWR or O_WRONLY is given) it will be
23321 truncated to length 0.
23324 The file is opened in append mode.
23327 The file is opened for reading only.
23330 The file is opened for writing only.
23333 The file is opened for reading and writing.
23336 Each other bit is silently ignored.
23341 @code{mode} is the bitwise or of the following values:
23345 User has read permission.
23348 User has write permission.
23351 Group has read permission.
23354 Group has write permission.
23357 Others have read permission.
23360 Others have write permission.
23363 Each other bit is silently ignored.
23368 @exdent Return value:
23369 open returns the new file descriptor or -1 if an error
23377 pathname already exists and O_CREAT and O_EXCL were used.
23380 pathname refers to a directory.
23383 The requested access is not allowed.
23386 pathname was too long.
23389 A directory component in pathname does not exist.
23392 pathname refers to a device, pipe, named pipe or socket.
23395 pathname refers to a file on a read-only filesystem and
23396 write access was requested.
23399 pathname is an invalid pointer value.
23402 No space on device to create the file.
23405 The process already has the maximum number of files open.
23408 The limit on the total number of files open on the system
23412 The call was interrupted by the user.
23416 @unnumberedsubsubsec close
23417 @cindex close, file-i/o system call
23426 @exdent Return value:
23427 close returns zero on success, or -1 if an error occurred.
23434 fd isn't a valid open file descriptor.
23437 The call was interrupted by the user.
23441 @unnumberedsubsubsec read
23442 @cindex read, file-i/o system call
23446 int read(int fd, void *buf, unsigned int count);
23449 Fread,fd,bufptr,count
23451 @exdent Return value:
23452 On success, the number of bytes read is returned.
23453 Zero indicates end of file. If count is zero, read
23454 returns zero as well. On error, -1 is returned.
23461 fd is not a valid file descriptor or is not open for
23465 buf is an invalid pointer value.
23468 The call was interrupted by the user.
23472 @unnumberedsubsubsec write
23473 @cindex write, file-i/o system call
23477 int write(int fd, const void *buf, unsigned int count);
23480 Fwrite,fd,bufptr,count
23482 @exdent Return value:
23483 On success, the number of bytes written are returned.
23484 Zero indicates nothing was written. On error, -1
23492 fd is not a valid file descriptor or is not open for
23496 buf is an invalid pointer value.
23499 An attempt was made to write a file that exceeds the
23500 host specific maximum file size allowed.
23503 No space on device to write the data.
23506 The call was interrupted by the user.
23510 @unnumberedsubsubsec lseek
23511 @cindex lseek, file-i/o system call
23515 long lseek (int fd, long offset, int flag);
23518 Flseek,fd,offset,flag
23521 @code{flag} is one of:
23525 The offset is set to offset bytes.
23528 The offset is set to its current location plus offset
23532 The offset is set to the size of the file plus offset
23537 @exdent Return value:
23538 On success, the resulting unsigned offset in bytes from
23539 the beginning of the file is returned. Otherwise, a
23540 value of -1 is returned.
23547 fd is not a valid open file descriptor.
23550 fd is associated with the @value{GDBN} console.
23553 flag is not a proper value.
23556 The call was interrupted by the user.
23560 @unnumberedsubsubsec rename
23561 @cindex rename, file-i/o system call
23565 int rename(const char *oldpath, const char *newpath);
23568 Frename,oldpathptr/len,newpathptr/len
23570 @exdent Return value:
23571 On success, zero is returned. On error, -1 is returned.
23578 newpath is an existing directory, but oldpath is not a
23582 newpath is a non-empty directory.
23585 oldpath or newpath is a directory that is in use by some
23589 An attempt was made to make a directory a subdirectory
23593 A component used as a directory in oldpath or new
23594 path is not a directory. Or oldpath is a directory
23595 and newpath exists but is not a directory.
23598 oldpathptr or newpathptr are invalid pointer values.
23601 No access to the file or the path of the file.
23605 oldpath or newpath was too long.
23608 A directory component in oldpath or newpath does not exist.
23611 The file is on a read-only filesystem.
23614 The device containing the file has no room for the new
23618 The call was interrupted by the user.
23622 @unnumberedsubsubsec unlink
23623 @cindex unlink, file-i/o system call
23627 int unlink(const char *pathname);
23630 Funlink,pathnameptr/len
23632 @exdent Return value:
23633 On success, zero is returned. On error, -1 is returned.
23640 No access to the file or the path of the file.
23643 The system does not allow unlinking of directories.
23646 The file pathname cannot be unlinked because it's
23647 being used by another process.
23650 pathnameptr is an invalid pointer value.
23653 pathname was too long.
23656 A directory component in pathname does not exist.
23659 A component of the path is not a directory.
23662 The file is on a read-only filesystem.
23665 The call was interrupted by the user.
23669 @unnumberedsubsubsec stat/fstat
23670 @cindex fstat, file-i/o system call
23671 @cindex stat, file-i/o system call
23675 int stat(const char *pathname, struct stat *buf);
23676 int fstat(int fd, struct stat *buf);
23679 Fstat,pathnameptr/len,bufptr
23682 @exdent Return value:
23683 On success, zero is returned. On error, -1 is returned.
23690 fd is not a valid open file.
23693 A directory component in pathname does not exist or the
23694 path is an empty string.
23697 A component of the path is not a directory.
23700 pathnameptr is an invalid pointer value.
23703 No access to the file or the path of the file.
23706 pathname was too long.
23709 The call was interrupted by the user.
23713 @unnumberedsubsubsec gettimeofday
23714 @cindex gettimeofday, file-i/o system call
23718 int gettimeofday(struct timeval *tv, void *tz);
23721 Fgettimeofday,tvptr,tzptr
23723 @exdent Return value:
23724 On success, 0 is returned, -1 otherwise.
23731 tz is a non-NULL pointer.
23734 tvptr and/or tzptr is an invalid pointer value.
23738 @unnumberedsubsubsec isatty
23739 @cindex isatty, file-i/o system call
23743 int isatty(int fd);
23748 @exdent Return value:
23749 Returns 1 if fd refers to the @value{GDBN} console, 0 otherwise.
23756 The call was interrupted by the user.
23760 @unnumberedsubsubsec system
23761 @cindex system, file-i/o system call
23765 int system(const char *command);
23768 Fsystem,commandptr/len
23770 @exdent Return value:
23771 The value returned is -1 on error and the return status
23772 of the command otherwise. Only the exit status of the
23773 command is returned, which is extracted from the hosts
23774 system return value by calling WEXITSTATUS(retval).
23775 In case /bin/sh could not be executed, 127 is returned.
23782 The call was interrupted by the user.
23785 @node Protocol specific representation of datatypes
23786 @subsection Protocol specific representation of datatypes
23787 @cindex protocol specific representation of datatypes, in file-i/o protocol
23790 * Integral datatypes::
23796 @node Integral datatypes
23797 @unnumberedsubsubsec Integral datatypes
23798 @cindex integral datatypes, in file-i/o protocol
23800 The integral datatypes used in the system calls are
23803 int@r{,} unsigned int@r{,} long@r{,} unsigned long@r{,} mode_t @r{and} time_t
23806 @code{Int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
23807 implemented as 32 bit values in this protocol.
23809 @code{Long} and @code{unsigned long} are implemented as 64 bit types.
23811 @xref{Limits}, for corresponding MIN and MAX values (similar to those
23812 in @file{limits.h}) to allow range checking on host and target.
23814 @code{time_t} datatypes are defined as seconds since the Epoch.
23816 All integral datatypes transferred as part of a memory read or write of a
23817 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
23820 @node Pointer values
23821 @unnumberedsubsubsec Pointer values
23822 @cindex pointer values, in file-i/o protocol
23824 Pointers to target data are transmitted as they are. An exception
23825 is made for pointers to buffers for which the length isn't
23826 transmitted as part of the function call, namely strings. Strings
23827 are transmitted as a pointer/length pair, both as hex values, e.g.@:
23834 which is a pointer to data of length 18 bytes at position 0x1aaf.
23835 The length is defined as the full string length in bytes, including
23836 the trailing null byte. Example:
23839 ``hello, world'' at address 0x123456
23850 @unnumberedsubsubsec struct stat
23851 @cindex struct stat, in file-i/o protocol
23853 The buffer of type struct stat used by the target and @value{GDBN} is defined
23858 unsigned int st_dev; /* device */
23859 unsigned int st_ino; /* inode */
23860 mode_t st_mode; /* protection */
23861 unsigned int st_nlink; /* number of hard links */
23862 unsigned int st_uid; /* user ID of owner */
23863 unsigned int st_gid; /* group ID of owner */
23864 unsigned int st_rdev; /* device type (if inode device) */
23865 unsigned long st_size; /* total size, in bytes */
23866 unsigned long st_blksize; /* blocksize for filesystem I/O */
23867 unsigned long st_blocks; /* number of blocks allocated */
23868 time_t st_atime; /* time of last access */
23869 time_t st_mtime; /* time of last modification */
23870 time_t st_ctime; /* time of last change */
23874 The integral datatypes are conforming to the definitions given in the
23875 approriate section (see @ref{Integral datatypes}, for details) so this
23876 structure is of size 64 bytes.
23878 The values of several fields have a restricted meaning and/or
23885 st_ino: No valid meaning for the target. Transmitted unchanged.
23887 st_mode: Valid mode bits are described in Appendix C. Any other
23888 bits have currently no meaning for the target.
23890 st_uid: No valid meaning for the target. Transmitted unchanged.
23892 st_gid: No valid meaning for the target. Transmitted unchanged.
23894 st_rdev: No valid meaning for the target. Transmitted unchanged.
23896 st_atime, st_mtime, st_ctime:
23897 These values have a host and file system dependent
23898 accuracy. Especially on Windows hosts the file systems
23899 don't support exact timing values.
23902 The target gets a struct stat of the above representation and is
23903 responsible to coerce it to the target representation before
23906 Note that due to size differences between the host and target
23907 representation of stat members, these members could eventually
23908 get truncated on the target.
23910 @node struct timeval
23911 @unnumberedsubsubsec struct timeval
23912 @cindex struct timeval, in file-i/o protocol
23914 The buffer of type struct timeval used by the target and @value{GDBN}
23915 is defined as follows:
23919 time_t tv_sec; /* second */
23920 long tv_usec; /* microsecond */
23924 The integral datatypes are conforming to the definitions given in the
23925 approriate section (see @ref{Integral datatypes}, for details) so this
23926 structure is of size 8 bytes.
23929 @subsection Constants
23930 @cindex constants, in file-i/o protocol
23932 The following values are used for the constants inside of the
23933 protocol. @value{GDBN} and target are resposible to translate these
23934 values before and after the call as needed.
23945 @unnumberedsubsubsec Open flags
23946 @cindex open flags, in file-i/o protocol
23948 All values are given in hexadecimal representation.
23960 @node mode_t values
23961 @unnumberedsubsubsec mode_t values
23962 @cindex mode_t values, in file-i/o protocol
23964 All values are given in octal representation.
23981 @unnumberedsubsubsec Errno values
23982 @cindex errno values, in file-i/o protocol
23984 All values are given in decimal representation.
24009 EUNKNOWN is used as a fallback error value if a host system returns
24010 any error value not in the list of supported error numbers.
24013 @unnumberedsubsubsec Lseek flags
24014 @cindex lseek flags, in file-i/o protocol
24023 @unnumberedsubsubsec Limits
24024 @cindex limits, in file-i/o protocol
24026 All values are given in decimal representation.
24029 INT_MIN -2147483648
24031 UINT_MAX 4294967295
24032 LONG_MIN -9223372036854775808
24033 LONG_MAX 9223372036854775807
24034 ULONG_MAX 18446744073709551615
24037 @node File-I/O Examples
24038 @subsection File-I/O Examples
24039 @cindex file-i/o examples
24041 Example sequence of a write call, file descriptor 3, buffer is at target
24042 address 0x1234, 6 bytes should be written:
24045 <- @code{Fwrite,3,1234,6}
24046 @emph{request memory read from target}
24049 @emph{return "6 bytes written"}
24053 Example sequence of a read call, file descriptor 3, buffer is at target
24054 address 0x1234, 6 bytes should be read:
24057 <- @code{Fread,3,1234,6}
24058 @emph{request memory write to target}
24059 -> @code{X1234,6:XXXXXX}
24060 @emph{return "6 bytes read"}
24064 Example sequence of a read call, call fails on the host due to invalid
24065 file descriptor (EBADF):
24068 <- @code{Fread,3,1234,6}
24072 Example sequence of a read call, user presses Ctrl-C before syscall on
24076 <- @code{Fread,3,1234,6}
24081 Example sequence of a read call, user presses Ctrl-C after syscall on
24085 <- @code{Fread,3,1234,6}
24086 -> @code{X1234,6:XXXXXX}
24090 @include agentexpr.texi
24104 % I think something like @colophon should be in texinfo. In the
24106 \long\def\colophon{\hbox to0pt{}\vfill
24107 \centerline{The body of this manual is set in}
24108 \centerline{\fontname\tenrm,}
24109 \centerline{with headings in {\bf\fontname\tenbf}}
24110 \centerline{and examples in {\tt\fontname\tentt}.}
24111 \centerline{{\it\fontname\tenit\/},}
24112 \centerline{{\bf\fontname\tenbf}, and}
24113 \centerline{{\sl\fontname\tensl\/}}
24114 \centerline{are used for emphasis.}\vfill}
24116 % Blame: doc@cygnus.com, 1991.